"</tr><tr>".
-4. If the month has finished, but the table row is not yet full, add empty `"</tr><tr>".
+5. If the month has finished, but the table row is not yet full, add empty `
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
+ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
```
+````
When the browser does not know the width/height of an image (from tag attributes or CSS), then it assumes them to equal `0` until the image finishes loading.
-After the first load browser usually caches the image, and on next loads it will have the size immediately. But on the first load the value of `ball.offsetWidth` is `0`. That leads to wrong coordinates.
+So the value of `ball.offsetWidth` will be `0` until the image loads. That leads to wrong coordinates in the code above.
+
+After the first load, the browser usually caches the image, and on reloads it will have the size immediately. But on the first load the value of `ball.offsetWidth` is `0`.
We should fix that by adding `width/height` to ``, then the sequence is:
-1. `HTML` -> `BODY` -> `FORM` -> `DIV` (capturing phase, the first listener):
-2. `P` (target phrase, triggers two times, as we've set two listeners: capturing and bubbling)
-3. `DIV` -> `FORM` -> `BODY` -> `HTML` (bubbling phase, the second listener).
+1. `HTML` -> `BODY` -> `FORM` -> `DIV -> P` (capturing phase, the first listener):
+2. `P` -> `DIV` -> `FORM` -> `BODY` -> `HTML` (bubbling phase, the second listener).
+
+Please note, the `P` shows up twice, because we've set two listeners: capturing and bubbling. The target triggers at the end of the first and at the beginning of the second phase.
There's a property `event.eventPhase` that tells us the number of the phase on which the event was caught. But it's rarely used, because we usually know it in the handler.
@@ -190,7 +192,7 @@ There's a property `event.eventPhase` that tells us the number of the phase on w
If we `addEventListener(..., true)`, then we should mention the same phase in `removeEventListener(..., true)` to correctly remove the handler.
```
-````smart header="Listeners on same element and same phase run in their set order"
+````smart header="Listeners on the same element and same phase run in their set order"
If we have multiple event handlers on the same phase, assigned to the same element with `addEventListener`, they run in the same order as they are created:
```js
@@ -199,14 +201,20 @@ elem.addEventListener("click", e => alert(2));
```
````
+```smart header="The `event.stopPropagation()` during the capturing also prevents the bubbling"
+The `event.stopPropagation()` method and its sibling `event.stopImmediatePropagation()` can also be called on the capturing phase. Then not only the futher capturing is stopped, but the bubbling as well.
+
+In other words, normally the event goes first down ("capturing") and then up ("bubbling"). But if `event.stopPropagation()` is called during the capturing phase, then the event travel stops, no bubbling will occur.
+```
+
## Summary
When an event happens -- the most nested element where it happens gets labeled as the "target element" (`event.target`).
-- Then the event moves down from the document root to `event.target`, calling handlers assigned with `addEventListener(...., true)` on the way (`true` is a shorthand for `{capture: true}`).
+- Then the event moves down from the document root to `event.target`, calling handlers assigned with `addEventListener(..., true)` on the way (`true` is a shorthand for `{capture: true}`).
- Then handlers are called on the target element itself.
-- Then the event bubbles up from `event.target` up to the root, calling handlers assigned using `on Drag the ball. Mouse over here to see the date Date: ${new Date()} Date: ${new Date()}` may be suited for that exactly ` `, it knows everything about it, so it should get the chance first. Then its immediate parent also knows about the context, but a little bit less, and so on till the very top element that handles general concepts and runs the last.
+The same for event handlers. The code that set the handler on a particular element knows maximum details about the element and what it does. A handler on a particular ` ` may be suited for that exactly ` `, it knows everything about it, so it should get the chance first. Then its immediate parent also knows about the context, but a little bit less, and so on till the very top element that handles general concepts and runs the last one.
Bubbling and capturing lay the foundation for "event delegation" -- an extremely powerful event handling pattern that we study in the next chapter.
diff --git a/2-ui/2-events/02-bubbling-and-capturing/event-order-bubbling.svg b/2-ui/2-events/02-bubbling-and-capturing/event-order-bubbling.svg
index e3d74989..2ea88f08 100644
--- a/2-ui/2-events/02-bubbling-and-capturing/event-order-bubbling.svg
+++ b/2-ui/2-events/02-bubbling-and-capturing/event-order-bubbling.svg
@@ -1 +1 @@
-
\ No newline at end of file
+
\ No newline at end of file
diff --git a/2-ui/2-events/02-bubbling-and-capturing/eventflow.svg b/2-ui/2-events/02-bubbling-and-capturing/eventflow.svg
index e7db9bff..566064cd 100644
--- a/2-ui/2-events/02-bubbling-and-capturing/eventflow.svg
+++ b/2-ui/2-events/02-bubbling-and-capturing/eventflow.svg
@@ -1 +1 @@
-
\ No newline at end of file
+
\ No newline at end of file
diff --git a/2-ui/2-events/03-event-delegation/article.md b/2-ui/2-events/03-event-delegation/article.md
index 3d8beda0..88118374 100644
--- a/2-ui/2-events/03-event-delegation/article.md
+++ b/2-ui/2-events/03-event-delegation/article.md
@@ -1,11 +1,11 @@
# Event delegation
-Capturing and bubbling allow us to implement one of most powerful event handling patterns called *event delegation*.
+Capturing and bubbling allow us to implement one of the most powerful event handling patterns called *event delegation*.
The idea is that if we have a lot of elements handled in a similar way, then instead of assigning a handler to each of them -- we put a single handler on their common ancestor.
-In the handler we get `event.target`, see where the event actually happened and handle it.
+In the handler we get `event.target` to see where the event actually happened and handle it.
Let's see an example -- the [Ba-Gua diagram](http://en.wikipedia.org/wiki/Ba_gua) reflecting the ancient Chinese philosophy.
@@ -101,8 +101,8 @@ table.onclick = function(event) {
Explanations:
1. The method `elem.closest(selector)` returns the nearest ancestor that matches the selector. In our case we look for ` ` on the way up from the source element.
-2. If `event.target` is not inside any ` `, then the call returns `null`, and we don't have to do anything.
-3. In case of nested tables, `event.target` may be a ` ` lying outside of the current table. So we check if that's actually *our table's* ` `.
+2. If `event.target` is not inside any ` `, then the call returns immediately, as there's nothing to do.
+3. In case of nested tables, `event.target` may be a ` `, but lying outside of the current table. So we check if that's actually *our table's* ` `.
4. And, if it's so, then highlight it.
As the result, we have a fast, efficient highlighting code, that doesn't care about the total number of ` ` in the table.
@@ -121,7 +121,7 @@ The first idea may be to assign a separate handler to each button. But there's a
The handler reads the attribute and executes the method. Take a look at the working example:
-```html autorun height=60 run
+```html autorun height=60 run untrusted
```
-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 b74c13f1..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
@@ -4,9 +4,9 @@ Drag'n'Drop is a great interface solution. Taking something and dragging and dro
In the modern HTML standard there's a [section about Drag and Drop](https://html.spec.whatwg.org/multipage/interaction.html#dnd) with special events such as `dragstart`, `dragend`, and so on.
-These events are useful in that they allow us to solve simple tasks easily. For instance, they allow us to handle the drag'n'drop of "external" files into the browser, so we can take a file in the OS file-manager and drop it into the browser window, thereby giving JavaScript access to its contents.
+These events allow us to support special kinds of drag'n'drop, such as handling dragging a file from OS file-manager and dropping it into the browser window. Then JavaScript can access the contents of such files.
-But native Drag Events also have limitations. For instance, we can't limit dragging by a certain area. Also we can't make it "horizontal" or "vertical" only. And there are other drag'n'drop tasks that can't be done using that API. Also, mobile device support for such events is almost non-existant.
+But native Drag Events also have limitations. For instance, we can't prevent dragging from a certain area. Also we can't make the dragging "horizontal" or "vertical" only. And there are many other drag'n'drop tasks that can't be done using them. Also, mobile device support for such events is very weak.
So here we'll see how to implement Drag'n'Drop using mouse events.
@@ -14,26 +14,23 @@ So here we'll see how to implement Drag'n'Drop using mouse events.
The basic Drag'n'Drop algorithm looks like this:
-1. On `mousedown` - prepare the element for moving, if needed (maybe create a copy of it).
-2. Then on `mousemove` move it by changing `left/top` and `position:absolute`.
-3. On `mouseup` - perform all actions related to a finished Drag'n'Drop.
+1. On `mousedown` - prepare the element for moving, if needed (maybe create a clone of it, add a class to it or whatever).
+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 can extend it, for instance, by highlighting droppable (available for the drop) elements when hovering 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 algorithm for drag'n'drop of a ball:
+Here's the implementation of dragging a ball:
```js
-ball.onmousedown = function(event) { // (1) start the process
-
- // (2) prepare to moving: make absolute and on top by z-index
+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);
- // ...and put that absolutely positioned ball under the pointer
-
- moveAt(event.pageX, event.pageY);
+ document.body.append(ball);
// centers the ball at (pageX, pageY) coordinates
function moveAt(pageX, pageY) {
@@ -41,14 +38,17 @@ ball.onmousedown = function(event) { // (1) start the process
ball.style.top = pageY - ball.offsetHeight / 2 + 'px';
}
+ // move our absolutely positioned ball under the pointer
+ moveAt(event.pageX, event.pageY);
+
function onMouseMove(event) {
moveAt(event.pageX, event.pageY);
}
- // (3) move the ball on mousemove
+ // (2) move the ball on mousemove
document.addEventListener('mousemove', onMouseMove);
- // (4) drop the ball, remove unneeded handlers
+ // (3) drop the ball, remove unneeded handlers
ball.onmouseup = function() {
document.removeEventListener('mousemove', onMouseMove);
ball.onmouseup = null;
@@ -64,10 +64,10 @@ Here's an example in action:
[iframe src="ball" height=230]
-Try to drag'n'drop the mouse and you'll see such behavior.
+Try to drag'n'drop with the mouse and you'll see such behavior.
```
-That's because the browser has its own Drag'n'Drop for images and some other elements that runs automatically and conflicts with ours.
+That's because the browser has its own drag'n'drop support for images and some other elements. It runs automatically and conflicts with ours.
To disable it:
@@ -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 described above, so it should be easy to understand them now. Or roll our own, as you can see 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.view/index.html b/2-ui/3-event-details/4-mouse-drag-and-drop/ball.view/index.html
index 3fdd7fe7..8751c70a 100644
--- a/2-ui/3-event-details/4-mouse-drag-and-drop/ball.view/index.html
+++ b/2-ui/3-event-details/4-mouse-drag-and-drop/ball.view/index.html
@@ -13,16 +13,13 @@
+
+
+
diff --git a/2-ui/3-event-details/6-pointer-events/ball.view/index.html b/2-ui/3-event-details/6-pointer-events/ball.view/index.html
new file mode 100644
index 00000000..8bbef8f6
--- /dev/null
+++ b/2-ui/3-event-details/6-pointer-events/ball.view/index.html
@@ -0,0 +1,30 @@
+
+
+
+
+
+
+
+
diff --git a/2-ui/3-event-details/6-pointer-events/multitouch.view/index.html b/2-ui/3-event-details/6-pointer-events/multitouch.view/index.html
new file mode 100644
index 00000000..d46e1bc1
--- /dev/null
+++ b/2-ui/3-event-details/6-pointer-events/multitouch.view/index.html
@@ -0,0 +1,28 @@
+
+
+
+
+