Answers for "how to check if something is undefined javascript"

js if not undefined

if (typeof myVar !== "undefined") {
    console.log("myVar is DEFINED");
}

javascript check for undefined

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

javascript if undefined

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

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

} else if(comment === null){

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

}

test if is undefined javascript

let id;

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

if not undefined javascript

if(typeof myVar !== "undefined")

undefined javascript check

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