Introduction to variables:
Variables are used to store data values.
Declaring and assigning values to variables:
ex. var fullName = ‘John Doe’;
Here, we have declared a variable called “fullName” and stored value “John Doe” in it.
Best practice for naming the variables:
You can give variables names as you like. But, giving meaningful and descriptive variable names is a good programming practice.
Rules for declaring variables:
- All variables must be unique. They are also called as identifiers.
- You can create a variable containing letters, digits, underscore, and dollar sign.
- Variables can also start with _ and $.
- Variables are case sensitive. This means that variables names like “car” and “Car” are different.
- Javascript reserved keywords cannot be used as variables. Example: for, var, switch, try, catch. etc.
Expressions:
We can create expressions like algebraic expressions.
Example:
var a = 10;
var b = 20;
var c = a + b;
**Notes:
You can also declare a variable without giving value. But if you try to get value of that variable, you will get undefined.
You can also declare multiple variables in one statement.
Example: var firstName = “John”, lastName=”Doe”, gender=”Male”;
Simple Arithmetic Calculation program in javascript:
We will create a simple calculation program with the help of javascript variables and expressions.
Step1: Create an HTML file and paste the following code.
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Arithmetic Calculation</title>
<script type="text/javascript">
var a = 20, b = 10;
var addition = a + b;
var subtraction = a - b;
var multiplication = a * b;
var division = a / b;
document.write("Addition is :", addition);
document.write("<br />");
document.write("Subtraction is :", subtraction);
document.write("<br />");
document.write("Multiplication is :", multiplication);
document.write("<br />");
document.write("Division is :", division);
</script>
</head>
<body>
</body>
</html>Step 2: Open the HTML file in a browser. You will see the result as follows.
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