object of undefined code example

Example 1: how to check if object is undefined in javascript

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

Example 2: javacript detect undefined

//detecting undefined object property
if (typeof person.last_name === "undefined") {
    console.log("person last_name is undefined");
}

//detecting undefined variable 
if (typeof myVar === "undefined") {
    console.log("myVar is undefined");
}