ee1e8abd87
* feat(tools): add seed/solution restore script * chore(curriculum): remove empty sections' markers * chore(curriculum): add seed + solution to Chinese * chore: remove old formatter * fix: update getChallenges parse translated challenges separately, without reference to the source * chore(curriculum): add dashedName to English * chore(curriculum): add dashedName to Chinese * refactor: remove unused challenge property 'name' * fix: relax dashedName requirement * fix: stray tag Remove stray `pre` tag from challenge file. Signed-off-by: nhcarrigan <nhcarrigan@gmail.com> Co-authored-by: nhcarrigan <nhcarrigan@gmail.com>
84 lines
2.3 KiB
Markdown
84 lines
2.3 KiB
Markdown
---
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id: 587d78b2367417b2b2512b0e
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title: Add Items to an Array with push() and unshift()
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challengeType: 1
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forumTopicId: 301151
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dashedName: add-items-to-an-array-with-push-and-unshift
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---
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# --description--
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An array's length, like the data types it can contain, is not fixed. Arrays can be defined with a length of any number of elements, and elements can be added or removed over time; in other words, arrays are <dfn>mutable</dfn>. In this challenge, we will look at two methods with which we can programmatically modify an array: `Array.push()` and `Array.unshift()`.
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Both methods take one or more elements as parameters and add those elements to the array the method is being called on; the `push()` method adds elements to the end of an array, and `unshift()` adds elements to the beginning. Consider the following:
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```js
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let twentyThree = 'XXIII';
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let romanNumerals = ['XXI', 'XXII'];
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romanNumerals.unshift('XIX', 'XX');
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// now equals ['XIX', 'XX', 'XXI', 'XXII']
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romanNumerals.push(twentyThree);
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// now equals ['XIX', 'XX', 'XXI', 'XXII', 'XXIII']Notice that we can also pass variables, which allows us even greater flexibility in dynamically modifying our array's data.
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```
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# --instructions--
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We have defined a function, `mixedNumbers`, which we are passing an array as an argument. Modify the function by using `push()` and `unshift()` to add `'I', 2, 'three'` to the beginning of the array and `7, 'VIII', 9` to the end so that the returned array contains representations of the numbers 1-9 in order.
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# --hints--
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`mixedNumbers(["IV", 5, "six"])` should now return `["I", 2, "three", "IV", 5, "six", 7, "VIII", 9]`
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```js
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assert.deepEqual(mixedNumbers(['IV', 5, 'six']), [
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'I',
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2,
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'three',
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'IV',
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5,
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'six',
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7,
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'VIII',
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9
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]);
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```
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The `mixedNumbers` function should utilize the `push()` method
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```js
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assert(mixedNumbers.toString().match(/\.push/));
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```
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The `mixedNumbers` function should utilize the `unshift()` method
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```js
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assert(mixedNumbers.toString().match(/\.unshift/));
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```
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# --seed--
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## --seed-contents--
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```js
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function mixedNumbers(arr) {
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// Only change code below this line
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// Only change code above this line
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return arr;
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}
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console.log(mixedNumbers(['IV', 5, 'six']));
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```
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# --solutions--
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```js
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function mixedNumbers(arr) {
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arr.push(7,'VIII',9);
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arr.unshift('I',2,'three');
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return arr;
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}
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```
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