JavaScript Variables definition declaration with example

Variable definition – In programming, a variable is a value that can change, depending on conditions or on information passed to the program. In C Language variable is a named location in a memory where a program can manipulate the data. This location is used to hold the value of the variable. Its just like in Algebra,

X=5
Y=2
Z=x+y

Here X,Y and Z are variable , x value assigned to 5, y to 2 …. , All JavaScript variables must be identified with unique names called identifiers. Here x,y and z are identifier.

Commone Rules for creating names for variables (x,y,z ..) are :

Identifier Names can contain letters, digits, underscores, and dollar signs.
Identifier Names must begin with a letter (price,totalPrice,price2 …)
Identifier Names are case sensitive (x and X are different variables)
Reserved words (like JavaScript keywords) cannot be used as names
variable will declare with prefix var like var price

Example declaring variable
<script> var price = 100; (valid) var 2price= 100;(not valid) var person = "Aayush";(valid) </script>
We can also declare variable in single line like

var person = “Sanjay”, BikeName = “Bajaj Pulser”, price = 70000;

JavaScript Variables working Example

Create a page variable.html copy and paste below code and save and run.
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Variable Example</title> </head> <body> <input type="text" id="name" /> <br/> <input type="submit" onclick="variableAlert()" value="Submit"> </body> <script> function variableAlert(){ var name = document.getElementById('name').value; alert(name); } </script> </html>