fixes

1-js/05-data-types/06-iterable/article.md

@@ -3,9 +3,9 @@
 
 *Iterable* objects is a generalization of arrays. That's a concept that allows to make any object useable in a `for..of` loop.
 
-Of course, Arrays are iterable. But there are many other built-in objects, that are iterable as well. For instance, Strings are iterable also. As we'll see, many built-in operators and methods rely on them.
+Of course, Arrays are iterable. But there are many other built-in objects, that are iterable as well. For instance, strings are also iterable.
 
-If an object represents a collection (list, set) of something, then `for..of` is a great syntax to loop over it, so let's see how to make it work.
+If an object isn't technically an array, but represents a collection (list, set) of something, then `for..of` is a great syntax to loop over it, so let's see how to make it work.
 
 
 ## Symbol.iterator
@@ -31,9 +31,9 @@ To make the `range` iterable (and thus let `for..of` work) we need to add a meth
 1. When `for..of` starts, it calls that method once (or errors if not found). The method must return an *iterator* -- an object with the method `next`.
 2. Onward, `for..of` works *only with that returned object*.
 3. When `for..of` wants the next value, it calls `next()` on that object.
-4. The result of `next()` must have the form `{done: Boolean, value: any}`, where `done=true`  means that the iteration is finished, otherwise `value` must be the new value.
+4. The result of `next()` must have the form `{done: Boolean, value: any}`, where `done=true`  means that the iteration is finished, otherwise `value` is the next value.
 
-Here's the full implementation for `range`:
+Here's the full implementation for `range` with remarks:
 
 ```js run
 let range = {
@@ -68,10 +68,10 @@ for (let num of range) {
 }
 ```
 
-Please note the core feature of iterables: an important separation of concerns:
+Please note the core feature of iterables: separation of concerns.
 
 - The `range` itself does not have the `next()` method.
-- Instead, another object, a so-called "iterator" is created by the call to `range[Symbol.iterator]()`, and it handles the whole iteration.
+- Instead, another object, a so-called "iterator" is created by the call to `range[Symbol.iterator]()`, and its `next()` generates values for the iteration.
 
 So, the iterator object is separate from the object it iterates over.
 
@@ -140,9 +140,7 @@ for (let char of str) {
 
 ## Calling an iterator explicitly
 
-Normally, internals of iterables are hidden from the external code. There's a `for..of` loop, that works, that's all it needs to know.
-
-But to understand things a little bit deeper let's see how to create an iterator explicitly.
+For deeper understanding let's see how to use an iterator explicitly.
 
 We'll iterate over a string in exactlly the same way as `for..of`, but with direct calls. This code creates a string iterator and gets values from it "manually":
 
@@ -283,7 +281,7 @@ let str = '𝒳😂𩷶';
 
 alert( slice(str, 1, 3) ); // 😂𩷶
 
-// native method does not support surrogate pairs
+// the native method does not support surrogate pairs
 alert( str.slice(1, 3) ); // garbage (two pieces from different surrogate pairs)
 ```