javascript typeof undefined code example

Example 1: js if not undefined

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

Example 2: javascript if undefined

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

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

} else if(comment === null){

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

}

Example 3: javascript typeof undfined

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

Example 4: javascript type of undefined

if (typeof x == 'undefined'){
   // instructions
 }