JAVASCRIPT
JavaScript
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Overview
JavaScript was originally developed to determine what browser a web page was loading on. It is commonly referred to as the language which was “designed in a weekend” or “designed in 2 weeks” (both which are partial truths).
The most common use for JavaScript today is to enrich basic HTML webpages, as well as run back-end server tasks with a platform such as node.js. It can also be used to develop desktop applications with a platform such as nw.js or electron.
Adding JavaScript Code In An HTML Page
There are two basic ways to add Javascript code into a web page. You can either:
Include a JavaScript file (.js)
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Or include the JavaScript code directly into the web page:
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If adding a standalone javascript file, you can use the keyword defer to tell the browser to wait until the rest of the page has loaded before loading the Javascript file.
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Constants
Constants can’t really be defined in JavaScript, at least not in the way you can in C and C++. One of the easiest workarounds is to just you all-uppercase variable names, like you would in C, so people will know that it shouldn’t be changed.
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Chrome let’s you declare constants, but they are not that useful as they are not multi-browser compatible.
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Functions
You can return values from a function by using the return keyword.
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You can return multiple values easily by creating an object on the fly (this is called an object literal).
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Message Boxes
A simple message box can be created easily in JavaScript by using the alert()
function.
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The Console
Many browsers support writing to the console with the command console.log()
, in a similar manner that you would use printf
for C/C++ in a Linux environment. The added ability of console.log()
is that it can be passed most objects, and these will be printed with their own ToString()
method.
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Strings
Strings can be defined with either the "
or '
character. Both are allowed, to distinguish between HTML strings and JavaScript strings when JavaScript is wrapped in HTML. In this case, you need to use the '
character for JavaScript strings, and the "
character for HTML strings.
String To Number Conversion
You can use the native javascript function parseFloat()
.
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Note that there is no native parseDouble()
function.
However, be careful! Javascript has some very weird implicit conversion rules, as highlighted below:
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Credit for the above goes to https://i.imgur.com/6aclmM6.png.
The Maths Object
Like many languages, JavaScript has a Maths object which you can use to do basic mathematical operations with.
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Authors

This work is licensed under a Creative Commons Attribution 4.0 International License .