JavaScript is a client side scripting language which allows the programmer to add logic to their web pages.

That's the technical answer, anyway, but you don't want to know that, do you? What you want to know is - what can JavaScript do for me?

The answer is pretty easy : you can use it to make your site more sticky, more user friendly, and more worthwhile. Plus, it'll probably make you more money - if you're selling things, that is.

JavaScript helps you add a shopping cart. It'll help you add nice user interfaces to your pages. You can use it to make fun questionnaires, or validate order forms before they're sent to you.

JavaScript documents can change appearance (sometimes upon request from the visitor), they can display graphics - on demand - and be used to implement web-based games.

Sadly, though, they can't make coffee to keep you going as you add more functionality and pizazz to your online, Web 2.0, interactive catalog that thinks it's a sales page.

You need to know about programming. You won't get very far without knowing a little bit. Now, if you really want to get to know programming, the following is going to help you:


Programming Concepts and Principles

However, the basics are actually pretty straightforward.

JavaScript programming allows you to (a) do something, (b) do something if a condition is satisfied, or (c) do something over and over until it's time to stop.

Doing Something
Put your code in functions. It's easier like that. Oh, a function is just a bit of named code. You use it to tell the computer to do something, using an easy to remember name. An example of a function is:

function MakeBackgroundRed () {
// code to make the background red
}

Of course, we haven't put in the code to actually do the work. Instead we've put in a comment that tells us what should go in the function, when we get around to doing it.

Doing something conditionally.
This is like saying - if the background is white, make it red. Of course, we have to know how to tell if the background is white, but let's just assume we can do that, and worry about how later on. So, the if statement:

if ( backgroundColor == white ) {
MakeBackgroundRed();
}

Oh look, we used our named code to make the background red! That funny double-equals sign just means 'equality', as in : is the bit on the left of it the same as the bit on the right?

Other possible signs include != (not equals), < (less than), > (more than), <=, and >=.

Do something over and over and over...
Ah, yes. Looping. This is more difficult. There are a few kinds of loop. There's the 'loop until I tell you to stop', the 'loop while something is true', and the 'loop for a few times'. Arguably, you don't need to know about all three, but in the spirit of completeness, we'll look at them after a brief commercial break.

Welcome back.

A loop is a piece of code that is designed to be performed over and over again. Firstly, the for loop:

for ( i = 0; i < 10; i++) {
// do something
}

No prizes for guessing what the above does. Yup, it does something (as yet not specified) ten times. 0 through 9. The i is called a variable, because what it contains can vary. In this case, we set it to 0, check that it is less than 10, and then add 1 to it (that's the i++ bit).

Easy, isn't it? The other kind of loop worth knowing about is the do ... while loop. If we wanted to do the same as above in a do ... while loop, it'd look like this:

i = 0;
do {
// do something
i++;
while (i < 10);

One last note. We put a semicolon after each statement to tell the computer that we've finished with our instruction.

Ok, as far as understanding simple JavaScript goes, that's about all that you'll need. Of course, if you want to write JavaScript code, you'll need to learn a whole lot more.