Data Types in Javscript

There are following data types in javascript:

1. String

2. Number

3. Boolean

4. Null

5. Undefined

Description with Example(s):

      String Data Type:

When we assign some string value in a variable then that time variable data type is string.

Example:

var str="my name is mac";

Number Data Type:

When we assign following value in a variable then that variable data type is Number.

Example:

var num1 = 10; // integer value including positive and negative values

var num2 = 10.10; // float , decimal value

var num3 = 10e5; // exponential notation

Note: NAN (Not a Number) is used to check that variable is the number or not in javascript.
 

3.       Boolean Data Type:

When we assign a variable as value “true” or “false” then that variable data type is Boolean

Example:

var flag = true;

var flag2 = false;

We use this data type to check condition.

4.       null data type:

When we have a variable and we want to erase the existing value of a variable then that time we assign that variable to “null”.

Example:

var str="albert";

       str=null; //this erase the value of string to null, now str has null data type                (actually it is object data type that hold nothing)

5.       undefined data type:

When we declare a variable but never assign any value to it or use an object property that does not exists then that time variable return “undefined”.

Example:

var str; //when we use this variable then  it show undefined

alert(str);

var str = "test value";

alert(str.count); //it will show undefined because there no property count for the string data type