Essential Javascript / PDF

Essential Javascript / PDF

Sample of the pdf document 

Javascript is an interpreted language with a C like syntax. While many people brush the language off as nothing more than a browser scripting language, it actually supports many advanced concepts such as object-oriented-programing, recursion, lambda, and closures. It's a very approachable language for the beginner that quickly scales to be as powerful a tool as your skills allow.

This reference will cover the basic language constructs. This is not a beginner's guide to programming. This article focuses on bringing people who already know another programming language up to speed on Javascript methodology. Additionally, this is not an exhaustive language definition, it is a broad overview that will occasionally focus in on some more advanced concepts. It's here to get you started, other articles will focus on making you an expert.

Getting Started:

To dive into Javascript all you need is a simple text-editor and a browser. In windows, you can use notepad under your accessories and Linux and mac users have a similar editor. Simply create a blank HTML page as such…

Hello World!



Save the file then in your browser type in the file name you just created to see the results.

Javascript is interpreted so any changes you make to this file will show up instantly in the browser the moment you hit the reload button.


In-Line Javascript:

To define a Javascript block in your web page, simply use the following block of HTML.



You can place these script blocks anywhere on the page that you wish, there are some rules and conventions however. If you are generating dynamic content as the page loads you will want the script blocks to appear where you want their output to be. For instance, if I wanted to say "Hello World!" I would want my script block to appear in the area of my web page and not in the section.


Unless your scripts are generating output as the page loads, good practice says that you should place your scripts at the very bottom of your HTML. The reason for this is that each time the browser encounters a tags themselves in your external file or you will get errors.

The biggest advantage to having an external Javascript file is that once the file has been loaded, the script will hang around the browser's cache which means if the Javascript is loaded on one page then it's almost a sure thing that the next page on the site the user visits will be able to load the file from the browser's cache instead of having to reload it over the Internet (This is an incredibly fast and speedy process).

Including an external file is basically the same as doing an in-line script, the only difference is that you specify a filename, and there's no actual code between ...

When the browser encounters this block it will load common.js, evaluate it, and execute it. Like in-line scripts above you can place this block anywhere you need the script to be and like in-line scripts you should place these as close to the bottom of the web-page as you can get away with.

The only difference between in-line Javascript blocks and external Javascript blocks is that an external Javascript block will pause to load the external file. If you discount that one thing, there's no procedural difference between the two!

Essential Javascript / PDF