e4870c472a
* fix/update-es6-destructor-challenge: Added test - Added test incase during destructuring somebody pass and extra key * fix/update-es6-destructor-challenge: Fixed the test case per review comments -Cleaned up regex - Setup two cases one where additional assignment of variables before and then after - Did not put uppercase case CONSTANT checks because not related to question * fix: corrected tests
89 lines
2.8 KiB
Markdown
89 lines
2.8 KiB
Markdown
---
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id: 587d7b89367417b2b2512b49
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title: Use Destructuring Assignment to Assign Variables from Objects
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challengeType: 1
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---
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## Description
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<section id='description'>
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We saw earlier how spread operator can effectively spread, or unpack, the contents of the array.
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We can do something similar with objects as well. <dfn>Destructuring assignment</dfn> is special syntax for neatly assigning values taken directly from an object to variables.
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Consider the following ES5 code:
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<blockquote>var voxel = {x: 3.6, y: 7.4, z: 6.54 };<br>var x = voxel.x; // x = 3.6<br>var y = voxel.y; // y = 7.4<br>var z = voxel.z; // z = 6.54</blockquote>
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Here's the same assignment statement with ES6 destructuring syntax:
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<blockquote>const { x, y, z } = voxel; // x = 3.6, y = 7.4, z = 6.54</blockquote>
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If instead you want to store the values of <code>voxel.x</code> into <code>a</code>, <code>voxel.y</code> into <code>b</code>, and <code>voxel.z</code> into <code>c</code>, you have that freedom as well.
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<blockquote>const { x : a, y : b, z : c } = voxel; // a = 3.6, b = 7.4, c = 6.54</blockquote>
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You may read it as "get the field <code>x</code> and copy the value into <code>a</code>," and so on.
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</section>
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## Instructions
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<section id='instructions'>
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Use destructuring to obtain the average temperature for tomorrow from the input object <code>AVG_TEMPERATURES</code>, and assign value with key <code>tomorrow</code> to <code>tempOfTomorrow</code> in line.
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</section>
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## Tests
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<section id='tests'>
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```yml
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tests:
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- text: <code>getTempOfTmrw(AVG_TEMPERATURES)</code> should be <code>79</code>
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testString: assert(getTempOfTmrw(AVG_TEMPERATURES) === 79);
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- text: destructuring with reassignment was used
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testString: getUserInput => assert(code.match(/{[\S\s]*\w+\s*:[\S\s]*\w+\s*}\s*=\s*(avgTemperatures|AVG_TEMPERATURES)/));
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- text: The key <code>tomorrow</code> was destructured from <code>AVG_TEMPERATURES</code>
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testString: getUserInput => assert(code.match(/{[\S\s]*tomorrow\s*:\s*tempOfTomorrow[\S\s]*}\s*=\s*(avgTemperatures|AVG_TEMPERATURES)/));
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```
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</section>
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## Challenge Seed
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<section id='challengeSeed'>
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<div id='js-seed'>
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```js
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const AVG_TEMPERATURES = {
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today: 77.5,
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tomorrow: 79
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};
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function getTempOfTmrw(avgTemperatures) {
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"use strict";
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// change code below this line
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const tempOfTomorrow = undefined; // change this line
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// change code above this line
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return tempOfTomorrow;
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}
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console.log(getTempOfTmrw(AVG_TEMPERATURES)); // should be 79
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```
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</div>
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</section>
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## Solution
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<section id='solution'>
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```js
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const AVG_TEMPERATURES = {
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today: 77.5,
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tomorrow: 79
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};
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function getTempOfTmrw(avgTemperatures) {
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"use strict";
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// change code below this line
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const {tomorrow:tempOfTomorrow} = avgTemperatures; // change this line
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// change code above this line
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return tempOfTomorrow;
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}
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console.log(getTempOfTmrw(AVG_TEMPERATURES)); // should be 79
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```
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</section>
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