Rename snippets with potential naming conflicts

snippets/articles/s/javascript-generator-for-range.md

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+---
+title: Using JavaScript generator functions for ranges
+shortTitle: Generator functions for ranges
+type: story
+language: javascript
+tags: [function,array]
+author: chalarangelo
+cover: generator
+excerpt: Learn how to use JavaScript ES6 generators and iterators to iterate over ranges of numbers.
+dateModified: 2021-06-12T19:30:41+03:00
+---
+
+### Generator functions
+
+[JavaScript ES6 generators](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/function*) allow you to define functions that can be exited and later re-entered, while retaining their context (variable bindings). They are defined using `function*` (`function` keyword followed by an asterisk) and use `yield` expressions to return their result. For example:
+
+```js
+function* generateRange(end, start = 0, step = 1) {
+  let x = start - step;
+  while(x < end - step) yield x += step;
+}
+
+const gen5 = generateRange(5);
+let x = gen5.next();
+
+while (!x.done) {
+  console.log(x.value);
+  x = gen5.next();
+} // Logs: 0, 1, 2, 3, 4
+```
+
+In the above example, we define a generator function, `generateRange`, which will return each value between `start` and `end`, incrementing by `step` each time. We use the [generator object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Generator) to call `Generator.prototype.next()` until it returns `{value: undefined, done: true}` to iterate over the values the generator produces.
+
+### Symbol.iterator
+
+[`Symbol.iterator`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/iterator) specifies the default iterator for an object. Oftentimes, `Symbol.iterator` is implemented using a generator function. For example:
+
+```js
+const iterableXx = {
+  [Symbol.iterator]: function* () {
+    yield 1;
+    yield 2;
+  }
+};
+
+console.log([...iterableX]); // [1, 2]
+```
+
+As you can see in this example, the object is made iterable by assigning a generator function to its `Symbol.iterator` property. This can come especially handy, if you want to iterate over some arbitrary data or create an object that is iterable and uses a generator function under the hood.
+
+### Putting it all together
+
+Knowing how both concepts work, we can combine them to create a range generator, similar to Python or Ruby's ranges:
+
+```js
+const range = (end, start = 0, step = 1) => {
+  function* generateRange() {
+    let x = start - step;
+    while(x < end - step) yield x += step;
+  }
+  return {
+    [Symbol.iterator]: generateRange
+  };
+}
+
+console.log([...range(7)]); // [0, 1, 2, 3, 4, 5, 6]
+for (let i of range(8, 2, 2)) console.log(i); // Logs: 2, 4, 6
+```