wehub-resource-sync
dde272c4b8
i18n - Build Validation / Validate i18n Builds (24) (push) Has been cancelled
CI - Node.js / Lint (24) (push) Has been cancelled
CI - Node.js / Build (24) (push) Has been cancelled
CI - Node.js / Test (24) (push) Has been cancelled
CI - Node.js / Test - Upcoming Changes (24) (push) Has been cancelled
CI - Node.js / Test - i18n (italian, 24) (push) Has been cancelled
CI - Node.js / Test - i18n (portuguese, 24) (push) Has been cancelled
CD - Docker - GHCR Images / Build and Push Images (push) Has been cancelled
73 lines
1.6 KiB
Markdown
73 lines
1.6 KiB
Markdown
---
|
|
id: 56533eb9ac21ba0edf2244aa
|
|
title: Understanding Uninitialized Variables
|
|
challengeType: 1
|
|
forumTopicId: 18335
|
|
dashedName: understanding-uninitialized-variables
|
|
---
|
|
|
|
# --description--
|
|
|
|
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 <dfn>string</dfn> of `undefined`.
|
|
|
|
# --instructions--
|
|
|
|
Initialize the three variables `a`, `b`, and `c` with `5`, `10`, and `"I am a"` respectively so that they will not be `undefined`.
|
|
|
|
# --hints--
|
|
|
|
`a` should be defined and have a final value of `6`.
|
|
|
|
```js
|
|
assert(typeof a === 'number' && a === 6);
|
|
```
|
|
|
|
`b` should be defined and have a final value of `15`.
|
|
|
|
```js
|
|
assert(typeof b === 'number' && b === 15);
|
|
```
|
|
|
|
`c` should not contain `undefined` and should have a final value of the string `I am a String!`
|
|
|
|
```js
|
|
assert(!/undefined/.test(c) && c === 'I am a String!');
|
|
```
|
|
|
|
You should not change code below the specified comment.
|
|
|
|
```js
|
|
assert(
|
|
/a = a \+ 1;/.test(__helpers.removeJSComments(code)) &&
|
|
/b = b \+ 5;/.test(__helpers.removeJSComments(code)) &&
|
|
/c = c \+ " String!";/.test(__helpers.removeJSComments(code))
|
|
);
|
|
```
|
|
|
|
# --seed--
|
|
|
|
## --seed-contents--
|
|
|
|
```js
|
|
// Only change code below this line
|
|
var a;
|
|
var b;
|
|
var c;
|
|
// Only change code above this line
|
|
|
|
a = a + 1;
|
|
b = b + 5;
|
|
c = c + " String!";
|
|
```
|
|
|
|
# --solutions--
|
|
|
|
```js
|
|
var a = 5;
|
|
var b = 10;
|
|
var c = "I am a";
|
|
a = a + 1;
|
|
b = b + 5;
|
|
c = c + " String!";
|
|
```
|