check undefined javascript es6 code example

Example 1: javascript check for undefined

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

Example 2: javascript typeof undfined

var x;
if (typeof x === 'undefined') {
   // these statements execute
}

Example 3: undefined javascript check

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

Example 4: javascript assignment operator if undefined

const variable2 = variable1  || 'new';