js if exists in object code example

Example 1: javascript does key exist

var person={"name":"Billy","age":20}
person.hasOwnProperty("name"); // true
person.hasOwnProperty("sex"); // false

Example 2: how to check if object exists in javascript

if (typeof maybeObject != "undefined") {
   alert("GOT THERE");
}

Example 3: check if a key exists in an object javascript

"key" in obj // true, regardless of the actual value