Javascript Data Types and Variable Scope

JavaScript Data Types:

JavaScript Data Types are the types of values that can be represented and manipulated by JavaScript.

JavaScript Data Types List:

1. Numbers.
2. Strings.
3. Boolean.
4. Null.
5. Undefined.
6. Object.
7. Array.
8. RegExp.

JavaScript variables:

The variable is the name of a reserved memory location. In JavaScript, the var keyword is used to declare a variable.

Rules for declaring a JavaScript variable:

1. JavaScript variable name must begin with a letter, underscore, or dollar sign.
2. JavaScript variable names are case-sensitive.
3. JavaScript reserved keywords like abstract, boolean, etc can’t be used as JavaScript variable names.

JavaScript variable scope:

1. Local variable.
2. Global variable.

JavaScript Local variable:

A variable defined inside a function or block of JavaScript code is known as a local variable. It can be accessed only within that function or block.

JavaScript Local Variable Example:

<html>
<head>
<script>
function showNumber(){
//local variable
var num=10;
document.write(num);
}
showNumber();
</script>
</head>
<body>
</body>
</html>

Try it:

JS Bin on jsbin.com

JavaScript Global variable:

A variable defined outside a function or block of JavaScript code is known as a global variable. It can be accessed anywhere in JavaScript code

JavaScript Global Variable Example:

<script>
<html>
<head>
<script>
//Global variable
var num=10;
function showNumber(){
document.writeln(num);
}
function displayNumber(){
document.writeln(num);
}
showNumber();
displayNumber();
</script>
</head>
<body>
</body>
</html>

Try it:

JS Bin on jsbin.com