@@ -363,7 +363,7 @@ There are 6 main methods to search for nodes in DOM:
-By far the most used are `querySelector` and `querySelectorAll`, but `getElementBy*` can be sporadically helpful or found in the old scripts.
+By far the most used are `querySelector` and `querySelectorAll`, but `getElement(s)By*` can be sporadically helpful or found in the old scripts.
Besides that:
diff --git a/2-ui/1-document/05-basic-dom-node-properties/article.md b/2-ui/1-document/05-basic-dom-node-properties/article.md
index 76469c18..99dde5bc 100644
--- a/2-ui/1-document/05-basic-dom-node-properties/article.md
+++ b/2-ui/1-document/05-basic-dom-node-properties/article.md
@@ -10,7 +10,7 @@ Different DOM nodes may have different properties. For instance, an element node
Each DOM node belongs to the corresponding built-in class.
-The root of the hierarchy is [EventTarget](https://dom.spec.whatwg.org/#eventtarget), that is inherited by [Node](http://dom.spec.whatwg.org/#interface-node), and other DOM nodes inherit from it.
+The root of the hierarchy is [EventTarget](https://dom.spec.whatwg.org/#eventtarget), that is inherited by [Node](https://dom.spec.whatwg.org/#interface-node), and other DOM nodes inherit from it.
Here's the picture, explanations to follow:
@@ -18,16 +18,39 @@ Here's the picture, explanations to follow:
The classes are:
-- [EventTarget](https://dom.spec.whatwg.org/#eventtarget) -- is the root "abstract" class. Objects of that class are never created. It serves as a base, so that all DOM nodes support so-called "events", we'll study them later.
-- [Node](http://dom.spec.whatwg.org/#interface-node) -- is also an "abstract" class, serving as a base for DOM nodes. It provides the core tree functionality: `parentNode`, `nextSibling`, `childNodes` and so on (they are getters). Objects of `Node` class are never created. But there are concrete node classes that inherit from it, namely: `Text` for text nodes, `Element` for element nodes and more exotic ones like `Comment` for comment nodes.
-- [Element](http://dom.spec.whatwg.org/#interface-element) -- is a base class for DOM elements. It provides element-level navigation like `nextElementSibling`, `children` and searching methods like `getElementsByTagName`, `querySelector`. A browser supports not only HTML, but also XML and SVG. The `Element` class serves as a base for more specific classes: `SVGElement`, `XMLElement` and `HTMLElement`.
-- [HTMLElement](https://html.spec.whatwg.org/multipage/dom.html#htmlelement) -- is finally the basic class for all HTML elements. It is inherited by concrete HTML elements:
+- [EventTarget](https://dom.spec.whatwg.org/#eventtarget) -- is the root "abstract" class for everything.
+
+ Objects of that class are never created. It serves as a base, so that all DOM nodes support so-called "events", we'll study them later.
+
+- [Node](https://dom.spec.whatwg.org/#interface-node) -- is also an "abstract" class, serving as a base for DOM nodes.
+
+ It provides the core tree functionality: `parentNode`, `nextSibling`, `childNodes` and so on (they are getters). Objects of `Node` class are never created. But there are other classes that inherit from it (and so inherit the `Node` functionality).
+
+- [Document](https://dom.spec.whatwg.org/#interface-document), for historical reasons often inherited by `HTMLDocument` (though the latest spec doesn't dictate it) -- is a document as a whole.
+
+ The `document` global object belongs exactly to this class. It serves as an entry point to the DOM.
+
+- [CharacterData](https://dom.spec.whatwg.org/#interface-characterdata) -- an "abstract" class, inherited by:
+ - [Text](https://dom.spec.whatwg.org/#interface-text) -- the class corresponding to a text inside elements, e.g. `Hello` in `
Once upon a time there was a mother pig who had three little pigs.
-
The three little pigs grew so big that their mother said to them, "You are too big to live here any longer. You must go and build houses for yourselves. But take care that the wolf does not catch you."
+
The three little pigs grew so big that their mother said to them, "You are too big to live here any longer. You must go and build houses for yourselves. But take care that the wolf does not catch you."
The three little pigs set off. "We will take care that the wolf does not catch us," they said.
Once upon a time there was a mother pig who had three little pigs.
-
The three little pigs grew so big that their mother said to them, "You are too big to live here any longer. You must go and build houses for yourselves. But take care that the wolf does not catch you."
+
The three little pigs grew so big that their mother said to them, "You are too big to live here any longer. You must go and build houses for yourselves. But take care that the wolf does not catch you."
The three little pigs set off. "We will take care that the wolf does not catch us," they said.
diff --git a/2-ui/3-event-details/3-mousemove-mouseover-mouseout-mouseenter-mouseleave/2-hoverintent/solution.view/hoverIntent.js b/2-ui/3-event-details/3-mousemove-mouseover-mouseout-mouseenter-mouseleave/2-hoverintent/solution.view/hoverIntent.js
index 4e6e2a3e..7503ca9c 100644
--- a/2-ui/3-event-details/3-mousemove-mouseover-mouseout-mouseenter-mouseleave/2-hoverintent/solution.view/hoverIntent.js
+++ b/2-ui/3-event-details/3-mousemove-mouseover-mouseout-mouseenter-mouseleave/2-hoverintent/solution.view/hoverIntent.js
@@ -88,7 +88,7 @@ class HoverIntent {
if (speed < this.sensitivity) {
clearInterval(this.checkSpeedInterval);
this.isHover = true;
- this.over.call(this.elem, event);
+ this.over.call(this.elem);
} else {
// speed fast, remember new coordinates as the previous ones
this.prevX = this.lastX;
diff --git a/2-ui/3-event-details/3-mousemove-mouseover-mouseout-mouseenter-mouseleave/article.md b/2-ui/3-event-details/3-mousemove-mouseover-mouseout-mouseenter-mouseleave/article.md
index c7ac0d4d..d409c3f1 100644
--- a/2-ui/3-event-details/3-mousemove-mouseover-mouseout-mouseenter-mouseleave/article.md
+++ b/2-ui/3-event-details/3-mousemove-mouseover-mouseout-mouseenter-mouseleave/article.md
@@ -80,7 +80,7 @@ An important feature of `mouseout` -- it triggers, when the pointer moves from a
```
-If we're on `#parent` and then move the pointer deeper into `#child`, but we get `mouseout` on `#parent`!
+If we're on `#parent` and then move the pointer deeper into `#child`, we get `mouseout` on `#parent`!
diff --git a/2-ui/3-event-details/3-mousemove-mouseover-mouseout-mouseenter-mouseleave/mouseover-bubble-nested.svg b/2-ui/3-event-details/3-mousemove-mouseover-mouseout-mouseenter-mouseleave/mouseover-bubble-nested.svg
index 07830295..6044eff1 100644
--- a/2-ui/3-event-details/3-mousemove-mouseover-mouseout-mouseenter-mouseleave/mouseover-bubble-nested.svg
+++ b/2-ui/3-event-details/3-mousemove-mouseover-mouseout-mouseenter-mouseleave/mouseover-bubble-nested.svg
@@ -1 +1 @@
-
\ No newline at end of file
+
\ No newline at end of file
diff --git a/2-ui/3-event-details/3-mousemove-mouseover-mouseout-mouseenter-mouseleave/mouseover-mouseout-from-outside.svg b/2-ui/3-event-details/3-mousemove-mouseover-mouseout-mouseenter-mouseleave/mouseover-mouseout-from-outside.svg
index 07176ba2..22335b52 100644
--- a/2-ui/3-event-details/3-mousemove-mouseover-mouseout-mouseenter-mouseleave/mouseover-mouseout-from-outside.svg
+++ b/2-ui/3-event-details/3-mousemove-mouseover-mouseout-mouseenter-mouseleave/mouseover-mouseout-from-outside.svg
@@ -1 +1 @@
-
\ No newline at end of file
+
\ No newline at end of file
diff --git a/2-ui/3-event-details/3-mousemove-mouseover-mouseout-mouseenter-mouseleave/mouseover-mouseout-over-elems.svg b/2-ui/3-event-details/3-mousemove-mouseover-mouseout-mouseenter-mouseleave/mouseover-mouseout-over-elems.svg
index 262ddf59..437f03b1 100644
--- a/2-ui/3-event-details/3-mousemove-mouseover-mouseout-mouseenter-mouseleave/mouseover-mouseout-over-elems.svg
+++ b/2-ui/3-event-details/3-mousemove-mouseover-mouseout-mouseenter-mouseleave/mouseover-mouseout-over-elems.svg
@@ -1 +1 @@
-
\ No newline at end of file
+
\ No newline at end of file
diff --git a/2-ui/3-event-details/3-mousemove-mouseover-mouseout-mouseenter-mouseleave/mouseover-mouseout.svg b/2-ui/3-event-details/3-mousemove-mouseover-mouseout-mouseenter-mouseleave/mouseover-mouseout.svg
index 784f435d..1277ddff 100644
--- a/2-ui/3-event-details/3-mousemove-mouseover-mouseout-mouseenter-mouseleave/mouseover-mouseout.svg
+++ b/2-ui/3-event-details/3-mousemove-mouseover-mouseout-mouseenter-mouseleave/mouseover-mouseout.svg
@@ -1 +1 @@
-
\ No newline at end of file
+
\ No newline at end of file
diff --git a/2-ui/3-event-details/3-mousemove-mouseover-mouseout-mouseenter-mouseleave/mouseover-to-child.svg b/2-ui/3-event-details/3-mousemove-mouseover-mouseout-mouseenter-mouseleave/mouseover-to-child.svg
index b38d76fb..78210845 100644
--- a/2-ui/3-event-details/3-mousemove-mouseover-mouseout-mouseenter-mouseleave/mouseover-to-child.svg
+++ b/2-ui/3-event-details/3-mousemove-mouseover-mouseout-mouseenter-mouseleave/mouseover-to-child.svg
@@ -1 +1 @@
-
\ No newline at end of file
+
\ No newline at end of file
diff --git a/2-ui/3-event-details/3-mousemove-mouseover-mouseout-mouseenter-mouseleave/mouseoverout-fast.view/script.js b/2-ui/3-event-details/3-mousemove-mouseover-mouseout-mouseenter-mouseleave/mouseoverout-fast.view/script.js
index 6d87199c..5752e83a 100755
--- a/2-ui/3-event-details/3-mousemove-mouseover-mouseout-mouseenter-mouseleave/mouseoverout-fast.view/script.js
+++ b/2-ui/3-event-details/3-mousemove-mouseover-mouseout-mouseenter-mouseleave/mouseoverout-fast.view/script.js
@@ -3,7 +3,7 @@ parent.onmouseover = parent.onmouseout = parent.onmousemove = handler;
function handler(event) {
let type = event.type;
- while (type < 11) type += ' ';
+ while (type.length < 11) type += ' ';
log(type + " target=" + event.target.id)
return false;
diff --git a/2-ui/3-event-details/4-mouse-drag-and-drop/2-drag-heroes/solution.view/field.svg b/2-ui/3-event-details/4-mouse-drag-and-drop/2-drag-heroes/solution.view/field.svg
index ca8bbc3b..f5bd9f4f 100644
--- a/2-ui/3-event-details/4-mouse-drag-and-drop/2-drag-heroes/solution.view/field.svg
+++ b/2-ui/3-event-details/4-mouse-drag-and-drop/2-drag-heroes/solution.view/field.svg
@@ -1 +1 @@
-
\ No newline at end of file
+
\ No newline at end of file
diff --git a/2-ui/3-event-details/4-mouse-drag-and-drop/article.md b/2-ui/3-event-details/4-mouse-drag-and-drop/article.md
index a47bfade..4c928eef 100644
--- a/2-ui/3-event-details/4-mouse-drag-and-drop/article.md
+++ b/2-ui/3-event-details/4-mouse-drag-and-drop/article.md
@@ -18,19 +18,19 @@ The basic Drag'n'Drop algorithm looks like this:
2. Then on `mousemove` move it by changing `left/top` with `position:absolute`.
3. On `mouseup` - perform all actions related to finishing the drag'n'drop.
-These are the basics. Later we'll see how to other features, such as highlighting current underlying elements while we drag over them.
+These are the basics. Later we'll see how to add other features, such as highlighting current underlying elements while we drag over them.
Here's the implementation of dragging a ball:
```js
-ball.onmousedown = function(event) {
+ball.onmousedown = function(event) {
// (1) prepare to moving: make absolute and on top by z-index
ball.style.position = 'absolute';
ball.style.zIndex = 1000;
// move it out of any current parents directly into body
// to make it positioned relative to the body
- document.body.append(ball);
+ document.body.append(ball);
// centers the ball at (pageX, pageY) coordinates
function moveAt(pageX, pageY) {
@@ -93,14 +93,14 @@ So we should listen on `document` to catch it.
## Correct positioning
-In the examples above the ball is always moved so, that it's center is under the pointer:
+In the examples above the ball is always moved so that its center is under the pointer:
```js
ball.style.left = pageX - ball.offsetWidth / 2 + 'px';
ball.style.top = pageY - ball.offsetHeight / 2 + 'px';
```
-Not bad, but there's a side-effect. To initiate the drag'n'drop, we can `mousedown` anywhere on the ball. But if "take" it from its edge, then the ball suddenly "jumps" to become centered under the mouse pointer.
+Not bad, but there's a side effect. To initiate the drag'n'drop, we can `mousedown` anywhere on the ball. But if "take" it from its edge, then the ball suddenly "jumps" to become centered under the mouse pointer.
It would be better if we keep the initial shift of the element relative to the pointer.
@@ -124,7 +124,7 @@ Let's update our algorithm:
```js
// onmousemove
- // ball has position:absoute
+ // ball has position:absolute
ball.style.left = event.pageX - *!*shiftX*/!* + 'px';
ball.style.top = event.pageY - *!*shiftY*/!* + 'px';
```
@@ -219,7 +219,7 @@ That's why the initial idea to put handlers on potential droppables doesn't work
So, what to do?
-There's a method called `document.elementFromPoint(clientX, clientY)`. It returns the most nested element on given window-relative coordinates (or `null` if given coordinates are out of the window).
+There's a method called `document.elementFromPoint(clientX, clientY)`. It returns the most nested element on given window-relative coordinates (or `null` if given coordinates are out of the window). If there are multiple overlapping elements on the same coordinates, then the topmost one is returned.
We can use it in any of our mouse event handlers to detect the potential droppable under the pointer, like this:
@@ -276,7 +276,7 @@ function onMouseMove(event) {
}
```
-In the example below when the ball is dragged over the soccer gate, the gate is highlighted.
+In the example below when the ball is dragged over the soccer goal, the goal is highlighted.
[codetabs height=250 src="ball4"]
@@ -300,4 +300,4 @@ We can lay a lot on this foundation.
- We can use event delegation for `mousedown/up`. A large-area event handler that checks `event.target` can manage Drag'n'Drop for hundreds of elements.
- And so on.
-There are frameworks that build architecture over it: `DragZone`, `Droppable`, `Draggable` and other classes. Most of them do the similar stuff to what's described above, so it should be easy to understand them now. Or roll your own, as you can see that that's easy enough to do, sometimes easier than adapting a third-part solution.
+There are frameworks that build architecture over it: `DragZone`, `Droppable`, `Draggable` and other classes. Most of them do the similar stuff to what's described above, so it should be easy to understand them now. Or roll your own, as you can see that that's easy enough to do, sometimes easier than adapting a third-party solution.
diff --git a/2-ui/3-event-details/4-mouse-drag-and-drop/ball_shift.svg b/2-ui/3-event-details/4-mouse-drag-and-drop/ball_shift.svg
index 3aa2541d..29fdb31e 100644
--- a/2-ui/3-event-details/4-mouse-drag-and-drop/ball_shift.svg
+++ b/2-ui/3-event-details/4-mouse-drag-and-drop/ball_shift.svg
@@ -1 +1 @@
-
\ No newline at end of file
+
\ No newline at end of file
diff --git a/2-ui/3-event-details/6-pointer-events/article.md b/2-ui/3-event-details/6-pointer-events/article.md
index 9d92144b..b8873e9d 100644
--- a/2-ui/3-event-details/6-pointer-events/article.md
+++ b/2-ui/3-event-details/6-pointer-events/article.md
@@ -8,23 +8,29 @@ Let's make a small overview, so that you understand the general picture and the
- Long ago, in the past, there were only mouse events.
- Then touch devices appeared. For the old code to work, they also generate mouse events. For instance, tapping generates `mousedown`. But mouse events were not good enough, as touch devices are more powerful in many aspects. For example, it's possible to touch multiple points at once, and mouse events don't have any properties for that.
+ Then touch devices became widespread, phones and tablets in particular. For the existing scripts to work, they generated (and still generate) mouse events. For instance, tapping a touchscreen generates `mousedown`. So touch devices worked well with web pages.
+
+ But touch devices have more capabilities than a mouse. For example, it's possible to touch multiple points at once ("multi-touch"). Although, mouse events don't have necessary properties to handle such multi-touches.
- So touch events were introduced, such as `touchstart`, `touchend`, `touchmove`, that have touch-specific properties (we don't cover them in detail here, because pointer events are even better).
- Still, it wasn't enough, as there are many other devices, such as pens, that have their own features. Also, writing code that listens for both touch and mouse events was cumbersome.
+ Still, it wasn't enough, as there are many other devices, such as pens, that have their own features. Also, writing code that listens for both touch and mouse events was cumbersome.
- To solve these issues, the new standard Pointer Events was introduced. It provides a single set of events for all kinds of pointing devices.
-As of now, [Pointer Events Level 2](https://www.w3.org/TR/pointerevents2/) specification is supported in all major browsers, while [Pointer Events Level 3](https://w3c.github.io/pointerevents/) is in the works. Unless you code for Internet Explorer 10, or for Safari 12 or below, there's no point in using mouse or touch events any more -- we can switch to pointer events.
+As of now, [Pointer Events Level 2](https://www.w3.org/TR/pointerevents2/) specification is supported in all major browsers, while the newer [Pointer Events Level 3](https://w3c.github.io/pointerevents/) is in the works and is mostly compatible with Pointer Events level 2.
-That being said, they have some important peculiarities that one should know in order to use them correctly and avoid surprises. We'll make note of them in this article.
+Unless you develop for old browsers, such as Internet Explorer 10, or for Safari 12 or below, there's no point in using mouse or touch events any more -- we can switch to pointer events.
+
+Then your code will work well with both touch and mouse devices.
+
+That said, there are some important peculiarities that one should know in order to use Pointer Events correctly and avoid surprises. We'll make note of them in this article.
## Pointer event types
Pointer events are named similarly to mouse events:
-| Pointer Event | Mouse event |
+| Pointer event | Similar mouse event |
|---------------|-------------|
| `pointerdown` | `mousedown` |
| `pointerup` | `mouseup` |
@@ -37,12 +43,12 @@ Pointer events are named similarly to mouse events:
| `gotpointercapture` | - |
| `lostpointercapture` | - |
-As we can see, for every `mouse`, there's a `pointer` that plays a similar role. Also there are 3 additional pointer events that don't have a corresponding `mouse...` counterpart, we'll explain them soon.
+As we can see, for every `mouse`, there's a `pointer` that plays a similar role. Also there are 3 additional pointer events that don't have a corresponding `mouse...` counterpart, we'll explain them soon.
```smart header="Replacing `mouse` with `pointer` in our code"
We can replace `mouse` events with `pointer` in our code and expect things to continue working fine with mouse.
-The support for touch devices will also "magically" improve, but we'll probably need to add `touch-action: none` in CSS. See the details below in the section about `pointercancel`.
+The support for touch devices will also "magically" improve. Although, we may need to add `touch-action: none` in some places in CSS. We'll cover it below in the section about `pointercancel`.
```
## Pointer event properties
@@ -50,22 +56,22 @@ The support for touch devices will also "magically" improve, but we'll probably
Pointer events have the same properties as mouse events, such as `clientX/Y`, `target`, etc., plus some others:
- `pointerId` - the unique identifier of the pointer causing the event.
-
- Allows us to handle multiple pointers, such as a touchscreen with stylus and multi-touch (explained below).
-- `pointerType` - the pointing device type. Must be a string, one of: "mouse", "pen" or "touch".
+
+ Browser-generated. Allows us to handle multiple pointers, such as a touchscreen with stylus and multi-touch (examples will follow).
+- `pointerType` - the pointing device type. Must be a string, one of: "mouse", "pen" or "touch".
We can use this property to react differently on various pointer types.
-- `isPrimary` - `true` for the primary pointer (the first finger in multi-touch).
+- `isPrimary` - is `true` for the primary pointer (the first finger in multi-touch).
-For pointers that measure contact area and pressure, e.g. a finger on the touchscreen, the additional properties can be useful:
+Some pointer devices measure contact area and pressure, e.g. for a finger on the touchscreen, there are additional properties for that:
-- `width` - the width of the area where the pointer touches the device. Where unsupported, e.g. for a mouse, it's always `1`.
+- `width` - the width of the area where the pointer (e.g. a finger) touches the device. Where unsupported, e.g. for a mouse, it's always `1`.
- `height` - the height of the area where the pointer touches the device. Where unsupported, it's always `1`.
- `pressure` - the pressure of the pointer tip, in range from 0 to 1. For devices that don't support pressure must be either `0.5` (pressed) or `0`.
- `tangentialPressure` - the normalized tangential pressure.
- `tiltX`, `tiltY`, `twist` - pen-specific properties that describe how the pen is positioned relative the surface.
-These properties aren't very well supported across devices, so they are rarely used. You can find the details in the [specification](https://w3c.github.io/pointerevents/#pointerevent-interface) if needed.
+These properties aren't supported by most devices, so they are rarely used. You can find the details about them in the [specification](https://w3c.github.io/pointerevents/#pointerevent-interface) if needed.
## Multi-touch
@@ -73,11 +79,11 @@ One of the things that mouse events totally don't support is multi-touch: a user
Pointer Events allow handling multi-touch with the help of the `pointerId` and `isPrimary` properties.
-Here's what happens when a user touches a screen in one place, then puts another finger somewhere else on it:
+Here's what happens when a user touches a touchscreen in one place, then puts another finger somewhere else on it:
-1. At the first touch:
+1. At the first finger touch:
- `pointerdown` with `isPrimary=true` and some `pointerId`.
-2. For the second finger and further touches:
+2. For the second finger and more fingers (assuming the first one is still touching):
- `pointerdown` with `isPrimary=false` and a different `pointerId` for every finger.
Please note: the `pointerId` is assigned not to the whole device, but for each touching finger. If we use 5 fingers to simultaneously touch the screen, we have 5 `pointerdown` events, each with their respective coordinates and a different `pointerId`.
@@ -91,53 +97,51 @@ Here's the demo that logs `pointerdown` and `pointerup` events:
[iframe src="multitouch" edit height=200]
-Please note: you must be using a touchscreen device, such as a phone or a tablet, to actually see the difference. For single-touch devices, such as a mouse, there'll be always same `pointerId` with `isPrimary=true`, for all pointer events.
+Please note: you must be using a touchscreen device, such as a phone or a tablet, to actually see the difference in `pointerId/isPrimary`. For single-touch devices, such as a mouse, there'll be always same `pointerId` with `isPrimary=true`, for all pointer events.
```
## Event: pointercancel
-We've mentioned the importance of `touch-action: none` before. Now let's explain why, as skipping this may cause our interfaces to malfunction.
+The `pointercancel` event fires when there's an ongoing pointer interaction, and then something happens that causes it to be aborted, so that no more pointer events are generated.
-The `pointercancel` event fires when there's an ongoing pointer interaction, and then something happens that causes it to be aborted, so that no more pointer events are generated.
-
-Such causes are:
-- The pointer device hardware was disabled.
-- The device orientation changed (tablet rotated).
+Such causes are:
+- The pointer device hardware was physically disabled.
+- The device orientation changed (tablet rotated).
- The browser decided to handle the interaction on its own, considering it a mouse gesture or zoom-and-pan action or something else.
We'll demonstrate `pointercancel` on a practical example to see how it affects us.
-Let's say we're impelementing drag'n'drop for a ball, just as in the beginning of the article .
+Let's say we're implementing drag'n'drop for a ball, just as in the beginning of the article .
Here is the flow of user actions and the corresponding events:
-1) The user presses the mouse button on an image, to start dragging
+1) The user presses on an image, to start dragging
- `pointerdown` event fires
-2) Then they start dragging the image
+2) Then they start moving the pointer (thus dragging the image)
- `pointermove` fires, maybe several times
-3) Surprise! The browser has native drag'n'drop support for images, that kicks in and takes over the drag'n'drop process, thus generating `pointercancel` event.
+3) And then the surprise happens! The browser has native drag'n'drop support for images, that kicks in and takes over the drag'n'drop process, thus generating `pointercancel` event.
- The browser now handles drag'n'drop of the image on its own. The user may even drag the ball image out of the browser, into their Mail program or a File Manager.
- No more `pointermove` events for us.
-So the issue is that the browser "hijacks" the interaction: `pointercancel` fires and no more `pointermove` events are generated.
+So the issue is that the browser "hijacks" the interaction: `pointercancel` fires in the beginning of the "drag-and-drop" process, and no more `pointermove` events are generated.
```online
-Here's the demo with pointer events (only `up/down`, `move` and `cancel`) logged in the textarea:
+Here's the drag'n'drop demo with loggin of pointer events (only `up/down`, `move` and `cancel`) in the `textarea`:
[iframe src="ball" height=240 edit]
```
-We'd like to implement our own drag'n'drop, so let's tell the browser not to take it over.
+We'd like to implement the drag'n'drop on our own, so let's tell the browser not to take it over.
-**Prevent default browser actions to avoid `pointercancel`.**
+**Prevent the default browser action to avoid `pointercancel`.**
We need to do two things:
1. Prevent native drag'n'drop from happening:
- We can do this by setting `ball.ondragstart = () => false`, just as described in the article .
- That works well for mouse events.
-2. For touch devices, there are also touch-related browser actions. We'll have problems with them too.
- - We can prevent them by setting `#ball { touch-action: none }` in CSS.
+2. For touch devices, there are other touch-related browser actions (besides drag'n'drop). To avoid problems with them too:
+ - Prevent them by setting `#ball { touch-action: none }` in CSS.
- Then our code will start working on touch devices.
After we do that, the events will work as intended, the browser won't hijack the process and doesn't emit `pointercancel`.
@@ -156,46 +160,79 @@ Now we can add the code to actually move the ball, and our drag'n'drop will work
Pointer capturing is a special feature of pointer events.
-The idea is that we can "bind" all events with a particular `pointerId` to a given element. Then all subsequent events with the same `pointerId` will be retargeted to the same element. That is: the browser sets that element as the target and trigger associated handlers, no matter where it actually happened.
+The idea is very simple, but may seem quite odd at first, as nothing like that exists for any other event type.
-The related methods are:
-- `elem.setPointerCapture(pointerId)` - binds the given `pointerId` to `elem`.
-- `elem.releasePointerCapture(pointerId)` - unbinds the given `pointerId` from `elem`.
+The main method is:
+- `elem.setPointerCapture(pointerId)` -- binds events with the given `pointerId` to `elem`. After the call all pointer events with the same `pointerId` will have `elem` as the target (as if happened on `elem`), no matter where in document they really happened.
-Such binding doesn't hold long. It's automatically removed after `pointerup` or `pointercancel` events, or when the target `elem` is removed from the document.
+In other words, `elem.setPointerCapture(pointerId)` retargets all subsequent events with the given `pointerId` to `elem`.
-Now when do we need this?
+The binding is removed:
+- automatically when `pointerup` or `pointercancel` events occur,
+- automatically when `elem` is removed from the document,
+- when `elem.releasePointerCapture(pointerId)` is called.
-**Pointer capturing is used to simplify drag'n'drop kind of interactions.**
+Now what is it good for? It's time to see a real-life example.
-Let's recall the problem we met while making a custom slider in the article .
+**Pointer capturing can be used to simplify drag'n'drop kind of interactions.**
-1) First, the user presses `pointerdown` on the slider thumb to start dragging it.
-2) ...But then, as they move the pointer, it may leave the slider: go below or over it.
+Let's recall how one can implement a custom slider, described in the .
-But we continue tracking track `pointermove` events and move the thumb until `pointerup`, even though the pointer is not on the slider any more.
+We can make a `slider` element to represent the strip and the "runner" (`thumb`) inside it:
-[Previously](info:mouse-drag-and-drop), to handle `pointermove` events that happen outside of the slider, we listened for `pointermove` events on the whole `document`.
+```html
+
+
+
+```
-Pointer capturing provides an alternative solution: we can call `thumb.setPointerCapture(event.pointerId)` in `pointerdown` handler, and then all future pointer events until `pointerup` will be retargeted to `thumb`.
+With styles, it looks like this:
-That is: events handlers on `thumb` will be called, and `event.target` will always be `thumb`, even if the user moves their pointer around the whole document. So we can listen at `thumb` for `pointermove`, no matter where it happens.
+[iframe src="slider-html" height=40 edit]
+
+
+
+And here's the working logic, as it was described, after replacing mouse events with similar pointer events:
+
+1. The user presses on the slider `thumb` -- `pointerdown` triggers.
+2. Then they move the pointer -- `pointermove` triggers, and our code moves the `thumb` element along.
+ - ...As the pointer moves, it may leave the slider `thumb` element, go above or below it. The `thumb` should move strictly horizontally, remaining aligned with the pointer.
+
+In the mouse event based solution, to track all pointer movements, including when it goes above/below the `thumb`, we had to assign `mousemove` event handler on the whole `document`.
+
+That's not a cleanest solution, though. One of the problems is that when a user moves the pointer around the document, it may trigger event handlers (such as `mouseover`) on some other elements, invoke totally unrelated UI functionality, and we don't want that.
+
+This is the place where `setPointerCapture` comes into play.
+
+- We can call `thumb.setPointerCapture(event.pointerId)` in `pointerdown` handler,
+- Then future pointer events until `pointerup/cancel` will be retargeted to `thumb`.
+- When `pointerup` happens (dragging complete), the binding is removed automatically, we don't need to care about it.
+
+So, even if the user moves the pointer around the whole document, events handlers will be called on `thumb`. Nevertheless, coordinate properties of the event objects, such as `clientX/clientY` will still be correct - the capturing only affects `target/currentTarget`.
Here's the essential code:
```js
thumb.onpointerdown = function(event) {
- // retarget all pointer events (until pointerup) to me
+ // retarget all pointer events (until pointerup) to thumb
thumb.setPointerCapture(event.pointerId);
+
+ // start tracking pointer moves
+ thumb.onpointermove = function(event) {
+ // moving the slider: listen on the thumb, as all pointer events are retargeted to it
+ let newLeft = event.clientX - slider.getBoundingClientRect().left;
+ thumb.style.left = newLeft + 'px';
+ };
+
+ // on pointer up finish tracking pointer moves
+ thumb.onpointerup = function(event) {
+ thumb.onpointermove = null;
+ thumb.onpointerup = null;
+ // ...also process the "drag end" if needed
+ };
};
-thumb.onpointermove = function(event) {
- // move the slider: listen at thumb, as all events are retargeted to it
- let newLeft = event.clientX - slider.getBoundingClientRect().left;
- thumb.style.left = newLeft + 'px';
-};
-
-// note: no need to call thumb.releasePointerCapture,
+// note: no need to call thumb.releasePointerCapture,
// it happens on pointerup automatically
```
@@ -203,27 +240,43 @@ thumb.onpointermove = function(event) {
The full demo:
[iframe src="slider" height=100 edit]
+
+
+
+In the demo, there's also an additional element with `onmouseover` handler showing the current date.
+
+Please note: while you're dragging the thumb, you may hover over this element, and its handler *does not* trigger.
+
+So the dragging is now free of side effects, thanks to `setPointerCapture`.
```
-**As a summary: the code becomes cleaner as we don't need to add/remove handlers on the whole `document` any more. That's what pointer capturing does.**
-There are two associated pointer events:
+
+At the end, pointer capturing gives us two benefits:
+1. The code becomes cleaner as we don't need to add/remove handlers on the whole `document` any more. The binding is released automatically.
+2. If there are other pointer event handlers in the document, they won't be accidentally triggered by the pointer while the user is dragging the slider.
+
+### Pointer capturing events
+
+There's one more thing to mention here, for the sake of completeness.
+
+There are two events associated with pointer capturing:
- `gotpointercapture` fires when an element uses `setPointerCapture` to enable capturing.
- `lostpointercapture` fires when the capture is released: either explicitly with `releasePointerCapture` call, or automatically on `pointerup`/`pointercancel`.
## Summary
-Pointer events allow handling mouse, touch and pen events simultaneously.
+Pointer events allow handling mouse, touch and pen events simultaneously, with a single piece of code.
Pointer events extend mouse events. We can replace `mouse` with `pointer` in event names and expect our code to continue working for mouse, with better support for other device types.
-Remember to set `touch-events: none` in CSS for elements that we engage, otherwise the browser will hijack many types of touch interactions, and pointer events won't be generated.
+For drag'n'drops and complex touch interactions that the browser may decide to hijack and handle on its own - remember to cancel the default action on events and set `touch-action: none` in CSS for elements that we engage.
-Additional abilities of Pointer events are:
+Additional abilities of pointer events are:
- Multi-touch support using `pointerId` and `isPrimary`.
- Device-specific properties, such as `pressure`, `width/height`, and others.
- Pointer capturing: we can retarget all pointer events to a specific element until `pointerup`/`pointercancel`.
-As of now, pointer events are supported in all major browsers, so we can safely switch to them, as long as IE10- and Safari 12- are not needed. And even with those browsers, there are polyfills that enable the support of pointer events.
+As of now, pointer events are supported in all major browsers, so we can safely switch to them, especially if IE10- and Safari 12- are not needed. And even with those browsers, there are polyfills that enable the support of pointer events.
diff --git a/2-ui/3-event-details/6-pointer-events/slider-html.view/index.html b/2-ui/3-event-details/6-pointer-events/slider-html.view/index.html
new file mode 100644
index 00000000..781016f5
--- /dev/null
+++ b/2-ui/3-event-details/6-pointer-events/slider-html.view/index.html
@@ -0,0 +1,6 @@
+
+
+
+
+
diff --git a/2-ui/3-event-details/6-pointer-events/slider.view/style.css b/2-ui/3-event-details/6-pointer-events/slider.view/style.css
index 9b3d3b82..a84cd5e7 100644
--- a/2-ui/3-event-details/6-pointer-events/slider.view/style.css
+++ b/2-ui/3-event-details/6-pointer-events/slider.view/style.css
@@ -8,6 +8,7 @@
}
.thumb {
+ touch-action: none;
width: 10px;
height: 25px;
border-radius: 3px;
diff --git a/2-ui/3-event-details/7-keyboard-events/article.md b/2-ui/3-event-details/7-keyboard-events/article.md
index 617852cc..12fe6320 100644
--- a/2-ui/3-event-details/7-keyboard-events/article.md
+++ b/2-ui/3-event-details/7-keyboard-events/article.md
@@ -107,7 +107,7 @@ So, `event.code` may match a wrong character for unexpected layout. Same letters
To reliably track layout-dependent characters, `event.key` may be a better way.
-On the other hand, `event.code` has the benefit of staying always the same, bound to the physical key location, even if the visitor changes languages. So hotkeys that rely on it work well even in case of a language switch.
+On the other hand, `event.code` has the benefit of staying always the same, bound to the physical key location. So hotkeys that rely on it work well even in case of a language switch.
Do we want to handle layout-dependant keys? Then `event.key` is the way to go.
@@ -139,22 +139,25 @@ For instance, the `` below expects a phone number, so it does not accept
```html autorun height=60 run
```
-Please note that special keys, such as `key:Backspace`, `key:Left`, `key:Right`, `key:Ctrl+V`, do not work in the input. That's a side-effect of the strict filter `checkPhoneKey`.
+The `onkeydown` handler here uses `checkPhoneKey` to check for the key pressed. If it's valid (from `0..9` or one of `+-()`), then it returns `true`, otherwise `false`.
-Let's relax it a little bit:
+As we know, the `false` value returned from the event handler, assigned using a DOM property or an attribute, such as above, prevents the default action, so nothing appears in the `` for keys that don't pass the test. (The `true` value returned doesn't affect anything, only returning `false` matters)
+Please note that special keys, such as `key:Backspace`, `key:Left`, `key:Right`, do not work in the input. That's a side effect of the strict filter `checkPhoneKey`. These keys make it return `false`.
+
+Let's relax the filter a little bit by allowing arrow keys `key:Left`, `key:Right` and `key:Delete`, `key:Backspace`:
```html autorun height=60 run
@@ -162,7 +165,9 @@ function checkPhoneKey(key) {
Now arrows and deletion works well.
-...But we still can enter anything by using a mouse and right-click + Paste. So the filter is not 100% reliable. We can just let it be like that, because most of time it works. Or an alternative approach would be to track the `input` event -- it triggers after any modification. There we can check the new value and highlight/modify it when it's invalid.
+Even though we have the key filter, one still can enter anything using a mouse and right-click + Paste. Mobile devices provide other means to enter values. So the filter is not 100% reliable.
+
+The alternative approach would be to track the `oninput` event -- it triggers *after* any modification. There we can check the new `input.value` and modify it/highlight the `` when it's invalid. Or we can use both event handlers together.
## Legacy
@@ -170,6 +175,12 @@ In the past, there was a `keypress` event, and also `keyCode`, `charCode`, `whic
There were so many browser incompatibilities while working with them, that developers of the specification had no way, other than deprecating all of them and creating new, modern events (described above in this chapter). The old code still works, as browsers keep supporting them, but there's totally no need to use those any more.
+## Mobile Keyboards
+
+When using virtual/mobile keyboards, formally known as IME (Input-Method Editor), the W3C standard states that a KeyboardEvent's [`e.keyCode` should be `229`](https://www.w3.org/TR/uievents/#determine-keydown-keyup-keyCode) and [`e.key` should be `"Unidentified"`](https://www.w3.org/TR/uievents-key/#key-attr-values).
+
+While some of these keyboards might still use the right values for `e.key`, `e.code`, `e.keyCode`... when pressing certain keys such as arrows or backspace, there's no guarantee, so your keyboard logic might not always work on mobile devices.
+
## Summary
Pressing a key always generates a keyboard event, be it symbol keys or special keys like `key:Shift` or `key:Ctrl` and so on. The only exception is `key:Fn` key that sometimes presents on a laptop keyboard. There's no keyboard event for it, because it's often implemented on lower level than OS.
diff --git a/2-ui/3-event-details/7-keyboard-events/german-layout.svg b/2-ui/3-event-details/7-keyboard-events/german-layout.svg
index 8a880e8e..7ac9a400 100644
--- a/2-ui/3-event-details/7-keyboard-events/german-layout.svg
+++ b/2-ui/3-event-details/7-keyboard-events/german-layout.svg
@@ -1 +1 @@
-
\ No newline at end of file
+
\ No newline at end of file
diff --git a/2-ui/3-event-details/7-keyboard-events/keyboard-dump.view/index.html b/2-ui/3-event-details/7-keyboard-events/keyboard-dump.view/index.html
index 40106283..a0d5a4f4 100644
--- a/2-ui/3-event-details/7-keyboard-events/keyboard-dump.view/index.html
+++ b/2-ui/3-event-details/7-keyboard-events/keyboard-dump.view/index.html
@@ -28,7 +28,7 @@
-
+
diff --git a/2-ui/3-event-details/7-keyboard-events/keyboard-dump.view/script.js b/2-ui/3-event-details/7-keyboard-events/keyboard-dump.view/script.js
index 5eba24c7..d97f7a7b 100644
--- a/2-ui/3-event-details/7-keyboard-events/keyboard-dump.view/script.js
+++ b/2-ui/3-event-details/7-keyboard-events/keyboard-dump.view/script.js
@@ -5,6 +5,8 @@ let lastTime = Date.now();
function handle(e) {
if (form.elements[e.type + 'Ignore'].checked) return;
+ area.scrollTop = 1e6;
+
let text = e.type +
' key=' + e.key +
' code=' + e.code +
diff --git a/2-ui/3-event-details/7-keyboard-events/us-layout.svg b/2-ui/3-event-details/7-keyboard-events/us-layout.svg
index 699277e0..353f225f 100644
--- a/2-ui/3-event-details/7-keyboard-events/us-layout.svg
+++ b/2-ui/3-event-details/7-keyboard-events/us-layout.svg
@@ -1 +1 @@
-
\ No newline at end of file
+
\ No newline at end of file
diff --git a/2-ui/3-event-details/8-onscroll/1-endless-page/solution.md b/2-ui/3-event-details/8-onscroll/1-endless-page/solution.md
index 10945ccd..54c10119 100644
--- a/2-ui/3-event-details/8-onscroll/1-endless-page/solution.md
+++ b/2-ui/3-event-details/8-onscroll/1-endless-page/solution.md
@@ -55,11 +55,11 @@ function populate() {
// document bottom
let windowRelativeBottom = document.documentElement.getBoundingClientRect().bottom;
- // if the user scrolled far enough (<100px to the end)
- if (windowRelativeBottom < document.documentElement.clientHeight + 100) {
- // let's add more data
- document.body.insertAdjacentHTML("beforeend", `
Date: ${new Date()}
`);
- }
+ // if the user hasn't scrolled far enough (>100px to the end)
+ if (windowRelativeBottom > document.documentElement.clientHeight + 100) break;
+
+ // let's add more data
+ document.body.insertAdjacentHTML("beforeend", `
Date: ${new Date()}
`);
}
}
```
diff --git a/2-ui/3-event-details/8-onscroll/article.md b/2-ui/3-event-details/8-onscroll/article.md
index 7b5cf484..734bd84c 100644
--- a/2-ui/3-event-details/8-onscroll/article.md
+++ b/2-ui/3-event-details/8-onscroll/article.md
@@ -1,6 +1,6 @@
# Scrolling
-The `scroll` event allows to react on a page or element scrolling. There are quite a few good things we can do here.
+The `scroll` event allows reacting to a page or element scrolling. There are quite a few good things we can do here.
For instance:
- Show/hide additional controls or information depending on where in the document the user is.
@@ -34,4 +34,4 @@ If we add an event handler to these events and `event.preventDefault()` in it, t
There are many ways to initiate a scroll, so it's more reliable to use CSS, `overflow` property.
-Here are few tasks that you can solve or look through to see the applications on `onscroll`.
+Here are few tasks that you can solve or look through to see applications of `onscroll`.
diff --git a/2-ui/4-forms-controls/1-form-elements/article.md b/2-ui/4-forms-controls/1-form-elements/article.md
index 01af1f40..f22518d9 100644
--- a/2-ui/4-forms-controls/1-form-elements/article.md
+++ b/2-ui/4-forms-controls/1-form-elements/article.md
@@ -8,11 +8,11 @@ Working with forms will be much more convenient when we learn them.
Document forms are members of the special collection `document.forms`.
-That's a so-called "named collection": it's both named and ordered. We can use both the name or the number in the document to get the form.
+That's a so-called *"named collection"*: it's both named and ordered. We can use both the name or the number in the document to get the form.
```js no-beautify
-document.forms.my - the form with name="my"
-document.forms[0] - the first form in the document
+document.forms.my; // the form with name="my"
+document.forms[0]; // the first form in the document
```
When we have a form, then any element is available in the named collection `form.elements`.
@@ -36,9 +36,9 @@ For instance:
```
-There may be multiple elements with the same name, that's often the case with radio buttons.
+There may be multiple elements with the same name. This is typical with radio buttons and checkboxes.
-In that case `form.elements[name]` is a collection, for instance:
+In that case, `form.elements[name]` is a *collection*. For instance:
```html run height=40
