How to Check for ”undefined” in Javascript?


In JavaScript, you can check for undefined using the typeof operator or by comparing a variable to the undefined value. Here are examples of both methods:

Method 1: Using the typeof operator

if(typeof myVar === 'undefined'){
  // myVar is undefined

Method 2: Comparing to the undefined value

if(myVar === undefined){
  // myVar is undefined

Note: It is recommended to use the typeof operator to check for undefined, as comparing to the undefined value can lead to unexpected results if the variable has been previously assigned a value of undefined.

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