Naren Least Generic to Most Specific

Javascript Essentials

Looking into creating my own ASP.Net Control Extenders (like in the Ajax Control Toolkit), I found myself having to brush up on my Javascript. So here is a quick revision of what I (and maybe you too) need to remember.

Function declaration:

function SayHelloTo(nameStr) {

document.write('Hello ' + nameStr);

}

Function with return statement:

function add(x, y) {

return x + y;

}

Variable declaration within a function:

function add(x, y) {

var z = x+y;

return z;

}

Classes in Javascript:

function car(makeStr, modelStr, colourStr) {

this.make = makeStr;

this.model = modelStr;

this.colour = colourStr;

}

Note how the declaration of a class is exactly the same as declaring a function with the salient keyword being this in the declaration of the variables within the function.

To create an instance of an object:

car1 = new car('Toyota', 'Camry', 'Red');

To access a property within the object:

car1.make = 'Ford';

Class methods:

function drive()

{

with (this) document.write(make+' is going for a drive');

}

Once again, note the this keyword.

Declaring class methods as above is however expensive on memory as each car object has a corresponding drive object.

Functions and constants can instead be declared in what is called the prototype for a class:

car.prototype.drive = drive;

Constants may also be defined in the prototype:

car.prototype.topSpeed = 100;

A class prototype can also be declared all at once with the function bodies:

car.prototype =

{

drive : function()

{

document.write(this.make+' is going for a drive');

},stop : function()

{

document.write(this.make+' is stopping');

}

}

Happy Javascripting