undefined in javascript check code example

Example 1: javascript check for undefined

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

Example 2: test if is undefined javascript

let id;

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

Example 3: how to check if object is undefined in javascript

if (typeof something === "undefined") {
    alert("something is undefined");
}

Example 4: undefined javascript check

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