diff --git a/1-js/05-data-types/06-iterable/article.md b/1-js/05-data-types/06-iterable/article.md index 5e464ac2..018926f1 100644 --- a/1-js/05-data-types/06-iterable/article.md +++ b/1-js/05-data-types/06-iterable/article.md @@ -1,7 +1,7 @@ # Iterables -*Iterable* objects is a generalization of arrays. That's a concept that allows us to make any object useable in a `for..of` loop. +*Iterable* objects are a generalization of arrays. That's a concept that allows us 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 also iterable. @@ -26,7 +26,7 @@ let range = { // for(let num of range) ... num=1,2,3,4,5 ``` -To make the `range` iterable (and thus let `for..of` work) we need to add a method to the object named `Symbol.iterator` (a special built-in symbol just for that). +To make the `range` object iterable (and thus let `for..of` work) we need to add a method to the object named `Symbol.iterator` (a special built-in symbol just for that). 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*. @@ -140,7 +140,7 @@ for (let char of str) { ## Calling an iterator explicitly -For deeper understanding let's see how to use an iterator explicitly. +For deeper understanding, let's see how to use an iterator explicitly. We'll iterate over a string in exactly the same way as `for..of`, but with direct calls. This code creates a string iterator and gets values from it "manually": @@ -165,16 +165,16 @@ That is rarely needed, but gives us more control over the process than `for..of` ## Iterables and array-likes [#array-like] -There are two official terms that look similar, but are very different. Please make sure you understand them well to avoid the confusion. +Two official terms look similar, but are very different. Please make sure you understand them well to avoid the confusion. - *Iterables* are objects that implement the `Symbol.iterator` method, as described above. - *Array-likes* are objects that have indexes and `length`, so they look like arrays. -When we use JavaScript for practical tasks in browser or other environments, we may meet objects that are iterables or array-likes, or both. +When we use JavaScript for practical tasks in a browser or any other environment, we may meet objects that are iterables or array-likes, or both. For instance, strings are both iterable (`for..of` works on them) and array-like (they have numeric indexes and `length`). -But an iterable may be not array-like. And vice versa an array-like may be not iterable. +But an iterable may not be array-like. And vice versa an array-like may not be iterable. For example, the `range` in the example above is iterable, but not array-like, because it does not have indexed properties and `length`. @@ -293,7 +293,7 @@ alert( str.slice(1, 3) ); // garbage (two pieces from different surrogate pairs) Objects that can be used in `for..of` are called *iterable*. - Technically, iterables must implement the method named `Symbol.iterator`. - - The result of `obj[Symbol.iterator]()` is called an *iterator*. It handles the further iteration process. + - The result of `obj[Symbol.iterator]()` is called an *iterator*. It handles further iteration process. - An iterator must have the method named `next()` that returns an object `{done: Boolean, value: any}`, here `done:true` denotes the end of the iteration process, otherwise the `value` is the next value. - The `Symbol.iterator` method is called automatically by `for..of`, but we also can do it directly. - Built-in iterables like strings or arrays, also implement `Symbol.iterator`.