66 lines
2.5 KiB
Markdown
66 lines
2.5 KiB
Markdown
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---
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id: 587d7b85367417b2b2512b38
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title: Catch Use of Assignment Operator Instead of Equality Operator
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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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Branching programs, i.e. ones that do different things if certain conditions are met, rely on <code>if</code>, <code>else if</code>, and <code>else</code> statements in JavaScript. The condition sometimes takes the form of testing whether a result is equal to a value.
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This logic is spoken (in English, at least) as "if x equals y, then ..." which can literally translate into code using the <code>=</code>, or assignment operator. This leads to unexpected control flow in your program.
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As covered in previous challenges, the assignment operator (<code>=</code>) in JavaScript assigns a value to a variable name. And the <code>==</code> and <code>===</code> operators check for equality (the triple <code>===</code> tests for strict equality, meaning both value and type are the same).
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The code below assigns <code>x</code> to be 2, which evaluates as <code>true</code>. Almost every value on its own in JavaScript evaluates to <code>true</code>, except what are known as the "falsy" values: <code>false</code>, <code>0</code>, <code>""</code> (an empty string), <code>NaN</code>, <code>undefined</code>, and <code>null</code>.
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<blockquote>let x = 1;<br>let y = 2;<br>if (x = y) {<br> // this code block will run for any value of y (unless y were originally set as a falsy)<br>} else {<br> // this code block is what should run (but won't) in this example<br>}</blockquote>
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</section>
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## Instructions
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<section id='instructions'>
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Fix the condition so the program runs the right branch, and the appropriate value is assigned to <code>result</code>.
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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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- text: 'Your code should fix the condition so it checks for equality, instead of using assignment.'
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testString: 'assert(result == "Not equal!", "Your code should fix the condition so it checks for equality, instead of using assignment.");'
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- text: The condition can use either <code>==</code> or <code>===</code> to test for equality.
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testString: 'assert(code.match(/x\s*?===?\s*?y/g), "The condition can use either <code>==</code> or <code>===</code> to test for equality.");'
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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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let x = 7;
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let y = 9;
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let result = "to come";
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if(x = y) {
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result = "Equal!";
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} else {
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result = "Not equal!";
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}
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console.log(result);
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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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// solution required
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```
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</section>
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