Copy and paste code as it is, and save entire content as a new HTML page. Then load it on to your browser. Unless you see result, it'll be difficult to follow script if you do not have prior programming background. The first condition is, none of fields can be submitted blank. Click on submit button without entering anything and observe reaction.

Here, we are making ample use of recently learnt for(){.} loop. Then we have used function too, to carry out certain validations. Our main function, checkfields(), is associated with OnClick attribute of "Submit" button, that is, when you click on "Submit" button, this function gets triggered.

Some new terms in today's script are: true, false, charAt(), toString(), break, indexOf(), string.length, and orm.elements[ ].

A quick explanation to make things easier:

If at 10:30 pm, I say, "It is night", then

var fact='true'

and if I say at 10:30 pm that "It's afternoon", then

var fact='false'

Which explains use of true and false, which are also called Boolean operators, which means, a Boolean variable can either be true or false, but NEVER both.

Until we learn about arrays, every character in a string has an index position. For instance, if we have

var city="Delhi"

then city.charAt(0)="D", city.charAt(1)="e", city.charAt(2)="l"...city.charAt(4)="i".

toString(), converts another data type to a string data-type. For example,

var num1=31 var num2=21 var char1=num1.toString() var char2=num2.toString()

So,

num1+num2=52 and char1+char2=3221

In second case, instead of being added, variables are being concatenated, which indicates that they are strings, not numbers. We'll see its application later.

break, true to its name, breaks something. In this case, it breaks loop in which it occurs, and takes execution of program to line immediately after loop, without meeting condition required to complete loop.

indexOf() tells us about position of a particular character in a string. Look its use in following code:

var city="Delhi"

Referring to this code, city.indexOf("e") should give us a value 1 and city.indexOf("h") should give us a value 3. city.indexOf("z") should give us a value less than zero, indicating that it does not belong to given string.

String.length gives us length of string, for instance, if city="Delhi", then city.length would give us 5.

Again, elements[ ] is an array, and we haven't dealt with them yet, so we leave rest of explanation to next section.

I'm going to give you a small example.

Suppose your JavaScript file is "myjfuncs.js".

and it has a function to return bigger number of two supplied as parameters (you can simply start with function, no need to write

So when we use one of its functions in a JavaScript:

In this way, we can use all complex functions contained in myjfuncs.js file.