2018-09-30 23:01:58 +01:00
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---
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id: 56105e7b514f539506016a5e
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title: Count Backwards With a For Loop
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challengeType: 1
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2019-02-14 12:24:02 -05:00
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videoUrl: 'https://scrimba.com/c/c2R6BHa'
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2019-07-31 11:32:23 -07:00
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forumTopicId: 16808
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2021-01-13 03:31:00 +01:00
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dashedName: count-backwards-with-a-for-loop
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2018-09-30 23:01:58 +01:00
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---
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2020-11-27 19:02:05 +01:00
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# --description--
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2018-09-30 23:01:58 +01:00
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A for loop can also count backwards, so long as we can define the right conditions.
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2020-11-27 19:02:05 +01:00
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2021-01-21 10:44:10 -06:00
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In order to decrement by two each iteration, we'll need to change our `initialization`, `condition`, and `final-expression`.
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2020-11-27 19:02:05 +01:00
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We'll start at `i = 10` and loop while `i > 0`. We'll decrement `i` by 2 each loop with `i -= 2`.
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2019-05-17 06:20:30 -07:00
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```js
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var ourArray = [];
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2020-03-25 08:07:13 -07:00
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for (var i = 10; i > 0; i -= 2) {
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2019-05-17 06:20:30 -07:00
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ourArray.push(i);
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}
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```
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2020-11-27 19:02:05 +01:00
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`ourArray` will now contain `[10,8,6,4,2]`. Let's change our `initialization` and `final-expression` so we can count backward by twos by odd numbers.
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2018-09-30 23:01:58 +01:00
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2020-11-27 19:02:05 +01:00
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# --instructions--
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2018-09-30 23:01:58 +01:00
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2020-11-27 19:02:05 +01:00
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Push the odd numbers from 9 through 1 to `myArray` using a `for` loop.
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2018-09-30 23:01:58 +01:00
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2020-11-27 19:02:05 +01:00
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# --hints--
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2018-09-30 23:01:58 +01:00
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2020-11-27 19:02:05 +01:00
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You should be using a `for` loop for this.
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2018-09-30 23:01:58 +01:00
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2020-11-27 19:02:05 +01:00
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```js
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assert(/for\s*\([^)]+?\)/.test(code));
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```
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2018-09-30 23:01:58 +01:00
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2020-11-27 19:02:05 +01:00
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You should be using the array method `push`.
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2018-09-30 23:01:58 +01:00
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```js
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2020-11-27 19:02:05 +01:00
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assert(code.match(/myArray.push/));
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```
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2018-09-30 23:01:58 +01:00
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2020-11-27 19:02:05 +01:00
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`myArray` should equal `[9,7,5,3,1]`.
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2018-09-30 23:01:58 +01:00
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2020-11-27 19:02:05 +01:00
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```js
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assert.deepEqual(myArray, [9, 7, 5, 3, 1]);
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2018-09-30 23:01:58 +01:00
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```
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2020-11-27 19:02:05 +01:00
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# --seed--
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2018-09-30 23:01:58 +01:00
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2020-11-27 19:02:05 +01:00
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## --after-user-code--
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2018-09-30 23:01:58 +01:00
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```js
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2018-10-20 21:02:47 +03:00
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if(typeof myArray !== "undefined"){(function(){return myArray;})();}
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2018-09-30 23:01:58 +01:00
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```
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2020-11-27 19:02:05 +01:00
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## --seed-contents--
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2018-09-30 23:01:58 +01:00
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2020-11-27 19:02:05 +01:00
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```js
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// Setup
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var myArray = [];
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2018-09-30 23:01:58 +01:00
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2020-11-27 19:02:05 +01:00
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// Only change code below this line
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```
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2018-09-30 23:01:58 +01:00
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2020-11-27 19:02:05 +01:00
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# --solutions--
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2018-09-30 23:01:58 +01:00
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```js
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var myArray = [];
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for (var i = 9; i > 0; i -= 2) {
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myArray.push(i);
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}
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```
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