javascript - Detecting an undefined object property

What's the best way of checking if an object property in JavaScript is undefined?

Answer

Use:

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

If an object variable which have some properties you can use same thing like this:

if (typeof my_obj.someproperties === "undefined"){
    console.log('the property is not available...'); // print into console
}