How do I check if a variable is undefined in JavaScript

Question

I am facing a problem in js that is How do I check if a variable is undefined in JavaScript?

Answer 1

In JavaScript, you can check if a variable is undefined in several ways:

1.Using the typeof operator:

if (typeof variable === 'undefined') {

    console.log('Variable is undefined');

}

2. Using strict equality (===):

if (variable === undefined) {

    console.log('Variable is undefined');

}

3.Checking if variable is not undefined using void 0:

if (variable === void 0) {

    console.log('Variable is undefined');

}