135 lines
3.2 KiB
Markdown
135 lines
3.2 KiB
Markdown
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---
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id: 56533eb9ac21ba0edf2244ca
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title: Using Objects for Lookups
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challengeType: 1
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videoUrl: 'https://scrimba.com/c/cdBk8sM'
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forumTopicId: 18373
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---
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## Description
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<section id='description'>
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Objects can be thought of as a key/value storage, like a dictionary. If you have tabular data, you can use an object to "lookup" values rather than a <code>switch</code> statement or an <code>if/else</code> chain. This is most useful when you know that your input data is limited to a certain range.
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Here is an example of a simple reverse alphabet lookup:
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```js
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var alpha = {
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1:"Z",
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2:"Y",
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3:"X",
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4:"W",
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...
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24:"C",
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25:"B",
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26:"A"
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};
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alpha[2]; // "Y"
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alpha[24]; // "C"
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var value = 2;
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alpha[value]; // "Y"
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```
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</section>
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## Instructions
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<section id='instructions'>
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Convert the switch statement into an object called <code>lookup</code>. Use it to look up <code>val</code> and assign the associated string to the <code>result</code> variable.
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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>phoneticLookup("alpha")</code> should equal <code>"Adams"</code>
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testString: assert(phoneticLookup("alpha") === 'Adams');
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- text: <code>phoneticLookup("bravo")</code> should equal <code>"Boston"</code>
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testString: assert(phoneticLookup("bravo") === 'Boston');
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- text: <code>phoneticLookup("charlie")</code> should equal <code>"Chicago"</code>
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testString: assert(phoneticLookup("charlie") === 'Chicago');
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- text: <code>phoneticLookup("delta")</code> should equal <code>"Denver"</code>
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testString: assert(phoneticLookup("delta") === 'Denver');
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- text: <code>phoneticLookup("echo")</code> should equal <code>"Easy"</code>
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testString: assert(phoneticLookup("echo") === 'Easy');
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- text: <code>phoneticLookup("foxtrot")</code> should equal <code>"Frank"</code>
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testString: assert(phoneticLookup("foxtrot") === 'Frank');
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- text: <code>phoneticLookup("")</code> should equal <code>undefined</code>
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testString: assert(typeof phoneticLookup("") === 'undefined');
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- text: You should not modify the <code>return</code> statement
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testString: assert(code.match(/return\sresult;/));
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- text: You should not use <code>case</code>, <code>switch</code>, or <code>if</code> statements
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testString: assert(!/case|switch|if/g.test(code.replace(/([/]{2}.*)|([/][*][^/*]*[*][/])/g,'')));
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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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// Setup
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function phoneticLookup(val) {
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var result = "";
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// Only change code below this line
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switch(val) {
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case "alpha":
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result = "Adams";
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break;
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case "bravo":
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result = "Boston";
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break;
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case "charlie":
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result = "Chicago";
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break;
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case "delta":
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result = "Denver";
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break;
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case "echo":
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result = "Easy";
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break;
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case "foxtrot":
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result = "Frank";
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}
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// Only change code above this line
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return result;
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}
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phoneticLookup("charlie");
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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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function phoneticLookup(val) {
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var result = "";
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var lookup = {
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alpha: "Adams",
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bravo: "Boston",
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charlie: "Chicago",
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delta: "Denver",
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echo: "Easy",
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foxtrot: "Frank"
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};
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result = lookup[val];
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return result;
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}
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```
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</section>
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