typescript check if undefined code example

Example 1: javascript check for undefined

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

Example 2: typescript check undefined

if(myvar === undefined){
	console.log("I am undefined.");
}

Example 3: typescript null and undefined check

if(!!someValue)

Example 4: typescript null and undefined check

let x = foo?.bar.baz();