83 lines
2.4 KiB
Markdown
83 lines
2.4 KiB
Markdown
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---
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id: 56533eb9ac21ba0edf2244aa
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title: Understanding Uninitialized Variables
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localeTitle: Entendiendo las variables sin inicializar
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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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Cuando se declaran las variables de JavaScript, tienen un valor inicial de <code>undefined</code> . Si realiza una operación matemática en una variable <code>undefined</code> , su resultado será <code>NaN</code> que significa <dfn>"No es un número"</dfn> . Si concatena una cadena con una variable <code>undefined</code> , obtendrá una <dfn>cadena</dfn> literal de <code>"undefined"</code> .
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</section>
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## Instructions
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<section id='instructions'>
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Inicialice las tres variables <code>a</code> , <code>b</code> y <code>c</code> con <code>5</code> , <code>10</code> y <code>"I am a"</code> respectivamente para que no queden <code>undefined</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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tests:
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- text: <code>a</code> debe definirse y evaluarse para tener el valor de <code>6</code>
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testString: 'assert(typeof a === "number" && a === 6, "<code>a</code> should be defined and evaluated to have the value of <code>6</code>");'
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- text: <code>b</code> debe definirse y evaluarse para que tenga el valor de <code>15</code>
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testString: 'assert(typeof b === "number" && b === 15, "<code>b</code> should be defined and evaluated to have the value of <code>15</code>");'
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- text: <code>c</code> no debe contener <code>undefined</code> y debe tener el valor "I am a String!"
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testString: 'assert(!/undefined/.test(c) && c === "I am a String!", "<code>c</code> should not contain <code>undefined</code> and should have a value of "I am a String!"");'
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- text: No cambie el código debajo de la línea
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testString: 'assert(/a = a \+ 1;/.test(code) && /b = b \+ 5;/.test(code) && /c = c \+ " String!";/.test(code), "Do not change code below the line");'
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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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// Initialize these three variables
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var a;
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var b;
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var c;
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// Do not change code below this line
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a = a + 1;
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b = b + 5;
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c = c + " String!";
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```
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</div>
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### After Test
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<div id='js-teardown'>
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```js
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console.info('after the test');
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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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var a = 5;
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var b = 10;
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var c = "I am a";
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a = a + 1;
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b = b + 5;
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c = c + " String!";
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```
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</section>
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