null and undefined check in javascript screenshot

null and undefined check in javascript

This tutorial will cover diffrence between null & undefind and how to check null & undefined in JavaScript.

Diffrence between null & undefined

null is a special value that means "no value".You can assign "null" to any variables

undefind means, the variable not declared or value not assigned to variables.(Undefind will through error message)

check null & undefined in JavaScript

Below code will explain how to check variable is null or undefined in JavaScript

function isNull(data) {
    var isNotValid = false;
    try {
        if (typeof data === "undefined") {
            isNotValid = true;
        } else if (data === null) {
            isNotValid = true;
        }
    } catch (e) {
        isNotValid = true;
    }
    return isNotValid;
}