JavaScript undefined Property

The undefined property is used to check if a value is assigned to a variable or not. 

Syntax:

var x;
if (typeof x === "undefined") {
 txt = "x is undefined";
} else {
 txt = "x is defined";
}

Return Value: It returns 'defined' if the variable is assigned any value and 'undefined' if the variable is not assigned any value. More example code for the above property are as follows: 

Below are examples of the undefined Property.

Example 1: 

Output:

'a' is defined

Example 2: 

Output: 

👁 Image

Supported Browsers:

• Google Chrome
• Firefox
• Internet Explorer
• Opera
• Safari