80 lines
1.7 KiB
Markdown
80 lines
1.7 KiB
Markdown
---
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id: 56533eb9ac21ba0edf2244aa
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title: Understanding Uninitialized Variables
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challengeType: 1
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videoUrl: 'https://scrimba.com/c/cBa2JAL'
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forumTopicId: 18335
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dashedName: understanding-uninitialized-variables
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---
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# --description--
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When JavaScript variables are declared, they have an initial value of `undefined`. If you do a mathematical operation on an `undefined` variable your result will be `NaN` which means <dfn>"Not a Number"</dfn>. If you concatenate a string with an `undefined` variable, you will get a literal <dfn>string</dfn> of `undefined`.
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# --instructions--
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Initialize the three variables `a`, `b`, and `c` with `5`, `10`, and `"I am a"` respectively so that they will not be `undefined`.
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# --hints--
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`a` should be defined and evaluated to have the value of `6`.
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```js
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assert(typeof a === 'number' && a === 6);
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```
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`b` should be defined and evaluated to have the value of `15`.
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```js
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assert(typeof b === 'number' && b === 15);
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```
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`c` should not contain `undefined` and should have a value of the string `I am a String!`
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```js
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assert(!/undefined/.test(c) && c === 'I am a String!');
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```
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You should not change code below the specified comment.
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```js
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assert(
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/a = a \+ 1;/.test(code) &&
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/b = b \+ 5;/.test(code) &&
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/c = c \+ " String!";/.test(code)
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);
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```
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# --seed--
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## --after-user-code--
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```js
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(function(a,b,c){ return "a = " + a + ", b = " + b + ", c = '" + c + "'"; })(a,b,c);
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```
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## --seed-contents--
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```js
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// Only change code below this line
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var a;
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var b;
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var c;
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// Only change code above 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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# --solutions--
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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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