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fix: Clarify mutate array with const challenge (#15745)

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Instructions for Mutate an Array Declared with const was unclear and
included unnecessary learning materials. This commit aims to clarify the
instructions for what the challenge requires, and also add in missing
challenge tests.

Closes #14832
This commit is contained in:
Eric Leung 2017-08-11 13:06:35 -07:00 committed by Quincy Larson
parent 56b9349c37
commit 5522c64172
1 changed files with 11 additions and 10 deletions
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21
challenges/02-javascript-algorithms-and-data-structures/es6.json
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@ -138,29 +138,30 @@
"id": "587d7b87367417b2b2512b42",
"title": "Mutate an Array Declared with const",
"description": [
"The <code>const</code> declaration has many use-cases in modern JavaScript.",
"The <code>const</code> declaration has many use cases in modern JavaScript.",
"Some developers prefer to assign all their variables using <code>const</code> by default, unless they know they will need to reassign the value. Only in that case, they use <code>let</code>.",
"However, it is important to understand that objects (including arrays and functions) assigned to a variable using <code>const</code> are still mutable. Using the <code>const</code> declaration only prevents reassignment of the variable identifier.",
"<blockquote>\"use strict\";<br>const s = [5, 6, 7];<br>s = [1, 2, 3]; // throws error, trying to assign a const<br>s[7] = 45; // works just as it would with an array declared with var</blockquote>",
"As you can see, you can mutate the object (<code>[5, 6, 7]</code>) itself and the variable identifier (<code>s</code>) will still point to the altered array. Like all arrays, the array assigned to <code>s</code> is mutable, but because <code>const</code> was used, you cannot use the variable identifier, <code>s</code>, to point to a different array using the assignment operator.",
"To make an object immutable, you can use <code>Object.freeze()</code>.",
"<blockquote>\"use strict\";<br>const s = [5, 6, 7];<br>s = [1, 2, 3]; // throws error, trying to assign a const<br>s[2] = 45; // works just as it would with an array declared with var or let<br>console.log(s); // returns [5, 6, 45]</blockquote>",
"As you can see, you can mutate the object <code>[5, 6, 7]</code> itself and the variable <code>s</code> will still point to the altered array <code>[5, 6, 45]</code>. Like all arrays, the array elements in <code>s</code> are mutable, but because <code>const</code> was used, you cannot use the variable identifier <code>s</code> to point to a different array using the assignment operator.",
"<hr>",
"An array is declared as <code>const s = [5, 7, 2]</code>. Change the array to <code>[2, 5, 7]</code>.",
"An array is declared as <code>const s = [5, 7, 2]</code>. Change the array to <code>[2, 5, 7]</code> using various element assignment.",
"<strong>Note</strong><br>Don't forget to add <code>\"use strict\";</code> to the top of your code."
],
"challengeSeed": [
"const s = [ 5, 7, 2 ];",
"const s = [5, 7, 2];",
"// change code below this line",
"",
"s = [2, 5, 7];",
"",
"// change code above this line",
"// Test your code",
"console.log(s);"
],
"tests": [
"// Test user did not replace const keyword",
"// Test s is const",
"assert.deepEqual(s, [2, 5, 7], 'message: <code>s</code> should be equal to <code>[2, 5, 7]</code>.');",
"assert(!Object.isFrozen(s), 'message: <code>s</code> should not be frozen.');"
"assert(code.match(/const/g), 'message: Do not replace <code>const</code> keyword.');",
"assert(code.match(/const\\s+s/g), 'message: <code>s</code> is declared with <code>const</code>.');",
"assert(code.match(/const\\s+s\\s*?=\\s*?\\[\\s*?2\\s*?,\\s*?5\\s*?,\\s*?7\\s*?\\]\\s*?;/g), 'message: Do not change the original array declaration.');",
"assert.deepEqual(s, [2, 5, 7], 'message: <code>s</code> should be equal to <code>[2, 5, 7]</code>.');"
],
"type": "waypoint",
"releasedOn": "Feb 17, 2017",