freeCodeCamp/use-destructuring-assignment-to-assign-variables-from-objects.english.md at 39c43dbe8aa20648746c0f656c0e3028c3d1c386

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Randell Dawson 05f73ca409 fix(curriculum): Convert blockquote elements to triple backtick syntax for JavaScript Algorithms and Data Structures (#35992 )

* fix: convert js algorithms and data structures

* fix: revert some blocks back to blockquote

* fix: reverted comparison code block to blockquotes

* fix: change js to json

Co-Authored-By: Oliver Eyton-Williams <ojeytonwilliams@gmail.com>

* fix: convert various section to triple backticks

* fix: Make the formatting consistent for comparisons

2019-05-17 08:20:30 -05:00

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id, title, challengeType

id	title	challengeType
587d7b89367417b2b2512b49	Use Destructuring Assignment to Assign Variables from Objects	1

Description

We saw earlier how spread operator can effectively spread, or unpack, the contents of the array. We can do something similar with objects as well. Destructuring assignment is special syntax for neatly assigning values taken directly from an object to variables. Consider the following ES5 code:

var voxel = { x: 3.6, y: 7.4, z: 6.54 };
var x = voxel.x; // x = 3.6
var y = voxel.y; // y = 7.4
var z = voxel.z; // z = 6.54

Here's the same assignment statement with ES6 destructuring syntax:

const { x, y, z } = voxel; // x = 3.6, y = 7.4, z = 6.54

If instead you want to store the values of voxel.x into a, voxel.y into b, and voxel.z into c, you have that freedom as well.

const { x: a, y: b, z: c } = voxel; // a = 3.6, b = 7.4, c = 6.54

You may read it as "get the field x and copy the value into a," and so on.

Instructions

Use destructuring to obtain the average temperature for tomorrow from the input object AVG_TEMPERATURES, and assign value with key tomorrow to tempOfTomorrow in line.

Tests

tests:
  - text: <code>getTempOfTmrw(AVG_TEMPERATURES)</code> should be <code>79</code>
    testString: assert(getTempOfTmrw(AVG_TEMPERATURES) === 79);
  - text: destructuring with reassignment was used
    testString: getUserInput => assert(code.match(/{[\S\s]*\w+\s*:[\S\s]*\w+\s*}\s*=\s*(avgTemperatures|AVG_TEMPERATURES)/));
  - text: The key <code>tomorrow</code> was destructured from <code>AVG_TEMPERATURES</code>
    testString: getUserInput => assert(code.match(/{[\S\s]*tomorrow\s*:\s*tempOfTomorrow[\S\s]*}\s*=\s*(avgTemperatures|AVG_TEMPERATURES)/));

Challenge Seed

const AVG_TEMPERATURES = {
  today: 77.5,
  tomorrow: 79
};

function getTempOfTmrw(avgTemperatures) {
  "use strict";
  // change code below this line
  const tempOfTomorrow = undefined; // change this line
  // change code above this line
  return tempOfTomorrow;
}

console.log(getTempOfTmrw(AVG_TEMPERATURES)); // should be 79

Solution

const AVG_TEMPERATURES = {
  today: 77.5,
  tomorrow: 79
};

function getTempOfTmrw(avgTemperatures) {
  "use strict";
  // change code below this line
  const {tomorrow:tempOfTomorrow} = avgTemperatures; // change this line
  // change code above this line
  return tempOfTomorrow;
}

console.log(getTempOfTmrw(AVG_TEMPERATURES)); // should be 79

2.8 KiB Raw Blame History