Javascript check if undefined
snippet in javascript

Javascript check if undefined

user5851

if (typeof myVariable === 'undefined'){
    //myVariable is undefined
}

javascript check undefined

user5581

if(myVar === null) {
	console.log("Element is undefined");
}

javascript if undefined

user9373

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

  alert('Variable "comment" is undefined.');

} else if(comment === null){

  alert('Variable "comment" is null.');

}

javascript check if boolean is undefined

user8582

if (typeof myFlag !== "undefined") {
  // comes here whether myFlag is true or false but not defined
}

test if is undefined javascript

user530

let id;

if(typeof id === 'undefined') {
    console.log("id is undefined...");
}

js check if undefined

user6021

let foo = undefined
//will return true
typeof foo === 'undefined'