JavaScript Variable

Using a JavaScript variable we can store a value in a variable.

JavaScript variable types

There are two types of variables local and global in JavaScript. It is also known as JavaScript variable scope.

• local variable
• global variable.

Remember some variable declaring Point:

• Variable names should contain digits, alphabets and underscore and dollar characters.
• Start a variable with an alphabet.
• Uppercase and Lowercase are different. This means “number” and “NUMBER” are different.
• We can not use keywords as variable names. For example while, for etc.
• Only underscore is allowed. It should not contain a special symbol or blank space.
• Variable names should not be more than 255 characters.
• “var” keyword is used to declare variable names in JavaScript.

Correct variables

This is the correct way to declare a variable.

1. var x = 50;
2. var _value=“Jony”;

Incorrect variables

This is an incorrect way to declare a variable.

1. var 123=70;
2. var *aa=570;

JavaScript variables examples

The basic example of a variable.

1. <script>
2. var x = 50;
3. var y = 20;
4. var z=x+y;
5. document.write(z);
6. </script>

examples Output:

70

JavaScript local variable

When we define a variable inside a block or function then it is known as a  local variable. We can only access  within a block or function only.

.For example:

1. <script>
2. function number(){
3. var num=50;//local variable
4. }
5. </script>

JavaScript global variable

When we define a variable outside a block or function then it is known as a  global variable. We can access it from any function.

For example:

1. <script>
2. var number=50 ; // gloabal variable
3. function num1(){
4. document.writeln(number);
5. }
6. function num2(){
7. document.writeln(number);
8. }
9. num1(); //calling function
10. num2();
11. </script>

Learn More :

JavaScript Comment and Syntax