JavaScript Variables definition declaration with example

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>

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