How to use Variables in the javascript?

Hi friends in this post I am sharing javascript variables .Declaring variables is one of the important step in javascript

What is a variable?

Variable is used to store a value which can be used  when required.

Syntax of javascript variables

var x=1;

Example of javascript variable:

<p id="abc"></p>
<script>
var x=1;
var y = 2;
document.getElementById("abc").innerHTML = x+y;
</script>

Now you will get the output 3.
Note: We must declare semicolon at the end of variable name.

What will happen when you use same variable multiple times in javascript?

Copy and paste the below code in notepad and save as index.html .Then open with the browser.


<p id="abc"></p>
<script>
var x=1;
var x = 2;
var x = 3;
var x = 4;
var x = 5;
document.getElementById("abc").innerHTML = x;
</script>
You will get the output 5 .

(i.e) Javascript will display the last value given in x ,if the same variable declared for multiple times.

How to declare string in the javascript variables?

What is a string?

A string is a series of characters.For better understanding I can say it as words . Examples of string  are book,bag,vegetables.
String must be placed in between the single or double quotes . It’s your wish to use single or double quotes.

Example to describe how to declare string in javascript:

<p id="abc"></p>
<script>
var bookname="English";
document.getElementById("abc").innerHTML = bookname;
</script>

Here English is the string. bookname is the variable.

What will happen if we not using quotes in string?

Very simple.There will be no output .

What are the effects of with and without using quotes ?

Consider the below example ,

<p id="abc"></p>
<script>
var x='1';
var y = '2';
document.getElementById("abc").innerHTML = x+y;
</script>

Copy and paste the above code in notepad and save as index.html .Then open with the browser.
You will get the output 12 and not 3 . Because after using the quotes the values are considered as string and + symbol use the concatenate process like adding strings .

Also try the below example ,

<p id="abc"></p>
<script>
var x="english";
var y = "tamil";
document.getElementById("abc").innerHTML = "there are " +x+y+  " books"  ;
</script>

You will get output as there are englishtamil books .

Another example:

<p id="abc"></p>
<script>
var x=8;
var y = 9;
document.getElementById("abc").innerHTML = "there are " +x+y+  " books";
</script>

Note: Here I have used variable name values as numbers and not as string. But it will show 89 instead of 17
because x is concatenated with the string there are .

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