javascript how to check undefined code example

Example 1: js if not undefined

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

Example 2: javascript check for undefined

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

Example 3: test if is undefined javascript

let id;

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

Example 4: js check if undefined

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

Example 5: javascript check undefined

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