freeCodeCamp/curriculum/challenges/chinese/02-javascript-algorithms-and-data-structures/basic-javascript/iterate-with-javascript-for-loops.md

---
id: cf1111c1c11feddfaeb5bdef
title: Iterate with JavaScript For Loops
challengeType: 1
videoUrl: 'https://scrimba.com/c/c9yNVCe'
forumTopicId: 18219
dashedName: iterate-with-javascript-for-loops
---

# --description--

You can run the same code multiple times by using a loop.

The most common type of JavaScript loop is called a `for` loop because it runs "for" a specific number of times.

For loops are declared with three optional expressions separated by semicolons:

`for ([initialization]; [condition]; [final-expression])`

The `initialization` statement is executed one time only before the loop starts. It is typically used to define and setup your loop variable.

The `condition` statement is evaluated at the beginning of every loop iteration and will continue as long as it evaluates to `true`. When `condition` is `false` at the start of the iteration, the loop will stop executing. This means if `condition` starts as `false`, your loop will never execute.

The `final-expression` is executed at the end of each loop iteration, prior to the next `condition` check and is usually used to increment or decrement your loop counter.

In the following example we initialize with `i = 0` and iterate while our condition `i < 5` is true. We'll increment `i` by `1` in each loop iteration with `i++` as our `final-expression`.

```js
var ourArray = [];
for (var i = 0; i < 5; i++) {
  ourArray.push(i);
}
```

`ourArray` will now contain `[0,1,2,3,4]`.

# --instructions--

Use a `for` loop to work to push the values 1 through 5 onto `myArray`.

# --hints--

You should be using a `for` loop for this.

```js
assert(/for\s*\([^)]+?\)/.test(code));
```

`myArray` should equal `[1,2,3,4,5]`.

```js
assert.deepEqual(myArray, [1, 2, 3, 4, 5]);
```

# --seed--

## --after-user-code--

```js
if (typeof myArray !== "undefined"){(function(){return myArray;})();}
```

## --seed-contents--

```js
// Setup
var myArray = [];

// Only change code below this line
```

# --solutions--

```js
var myArray = [];
for (var i = 1; i < 6; i++) {
  myArray.push(i);
}
```