76 lines
1.5 KiB
Markdown
76 lines
1.5 KiB
Markdown
|
---
|
||
|
|
id: 56105e7b514f539506016a5e
|
||
|
|
title: Count Backwards With a For Loop
|
||
|
|
challengeType: 1
|
||
|
|
videoUrl: 'https://scrimba.com/c/c2R6BHa'
|
||
|
|
forumTopicId: 16808
|
||
|
|
dashedName: count-backwards-with-a-for-loop
|
||
|
|
---
|
||
|
|
|
||
|
|
# --description--
|
||
|
|
|
||
|
|
A for loop can also count backwards, so long as we can define the right conditions.
|
||
|
|
|
||
|
|
In order to decrement by two each iteration, we'll need to change our initialization, condition, and final expression.
|
||
|
|
|
||
|
|
We'll start at `i = 10` and loop while `i > 0`. We'll decrement `i` by 2 each loop with `i -= 2`.
|
||
|
|
|
||
|
|
```js
|
||
|
|
var ourArray = [];
|
||
|
|
for (var i = 10; i > 0; i -= 2) {
|
||
|
|
ourArray.push(i);
|
||
|
|
}
|
||
|
|
```
|
||
|
|
|
||
|
|
`ourArray` will now contain `[10,8,6,4,2]`. Let's change our initialization and final expression so we can count backwards by twos to create an array of descending odd numbers.
|
||
|
|
|
||
|
|
# --instructions--
|
||
|
|
|
||
|
|
Push the odd numbers from 9 through 1 to `myArray` using a `for` loop.
|
||
|
|
|
||
|
|
# --hints--
|
||
|
|
|
||
|
|
You should be using a `for` loop for this.
|
||
|
|
|
||
|
|
```js
|
||
|
|
assert(/for\s*\([^)]+?\)/.test(code));
|
||
|
|
```
|
||
|
|
|
||
|
|
You should be using the array method `push`.
|
||
|
|
|
||
|
|
```js
|
||
|
|
assert(code.match(/myArray.push/));
|
||
|
|
```
|
||
|
|
|
||
|
|
`myArray` should equal `[9,7,5,3,1]`.
|
||
|
|
|
||
|
|
```js
|
||
|
|
assert.deepEqual(myArray, [9, 7, 5, 3, 1]);
|
||
|
|
```
|
||
|
|
|
||
|
|
# --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 = 9; i > 0; i -= 2) {
|
||
|
|
myArray.push(i);
|
||
|
|
}
|
||
|
|
```
|