What is the main difference between window.onload and onDocumentReady?

Both functions are used to perform tasks when the page is loaded in the browser but they have important differences. Most importantly, "window.onload" will execute code when browser has loaded the DOM tree and all other resources like images, objects, etc, while onDocumentReady allows you to execute code when only the DOM tree has been built, without waiting for images to load. Thus, you can start scripting agains the DOM much quicker with onDocumentReady. Another important difference is that window.onload is not cross-browser compatible while using something like jQuery's document.ready() will work nicely on all browsers.

decodeURI(), encodeURI()

Many characters cannot be sent in a URL, but must be converted to their hex encoding. These functions are used to convert an entire URI (a superset of URL) to and from a format that can be sent via a URI.

<script type="text/javascript">

var uri = "http://www.google.com/search?q=sonofusion Taleyarkhan"

document.write("Original uri: "+uri);

document.write("<br />encoded: "+encodeURI(uri));

</script>

What's Prototypes for JavaScript?

Objects have "prototypes" from which they may inherit fields and functions.

<script type="text/javascript">

function movieToString() {

return("title: "+this.title+" director: "+this.director);

}

function movie(title, director) {

this.title = title;

this.director = director || "unknown"; //if null assign to "unknown"

this.toString = movieToString; //assign function to this method pointer

}

movie.prototype.isComedy = false; //add a field to the movie's prototype

var officeSpace = new movie("OfficeSpace");

var narnia = new movie("Narni","Andrew Adamson");

document.write(narnia.toString());

document.write("

Narnia a comedy? "+narnia.isComedy);

officeSpace.isComedy = true; //override the default just for this object

document.write("

Office Space a comedy? "+officeSpace.isComedy);

</script>

eval()?

The eval() method is incredibly powerful allowing you to execute snippets of code during execution.

<script type="text/javascript">

var USA_Texas_Austin = "521,289";

document.write("Population is "+eval("USA_"+"Texas_"+"Austin"));

</script>

This produces

Population is 521,289

How to create a function using function constructor?

The following example illustrates this

It creates a function called square with argument x and returns x multiplied by itself.

var square = new Function ("x","return x*x");

What does break and continue statements do?

Continue statement continues the current loop (if label not specified) in a new iteration whereas break statement exits the current loop

How to associate functions with objects using JavaScript?

Let's now create a custom "toString()" method for our movie object. We can embed the function directly in the object like this.

<script type="text/javascript">

function movie(title, director) {

this.title = title;

this.director = director;

this.toString = function movieToString() {

return("title: "+this.title+" director: "+this.director);

}

}

var narnia = new movie("Narni","Andrew Adamson");

document.write(narnia.toString());

</script>

This produces

title: Narni director: Andrew Adamson

Or we can use a previously defined function and assign it to a variable. Note that the name of the function is not followed by parenthesis, otherwise it would just execute the function and stuff the returned value into the variable.

<script type="text/javascript">

function movieToString() {

return("title: "+this.title+" director: "+this.director);

}

function movie(title, director) {

this.title = title;

this.director = director;

this.toString = movieToString; //assign function to this method pointer

}

var aliens = new movie("Aliens","Cameron");

document.write(aliens.toString());

</script>

This produces

title: Aliens director: Cameron