object key check value code example

Example 1: how to check if object has key javascript

myObj.hasOwnProperty('key') // it checks object for particular key and not on prototype

Example 2: check object has key javascript

Object.prototype.hasOwnProperty()

Example 3: js check if object key exists

var obj = { key: undefined };
obj["key"] !== undefined // false, but the key exists!

Example 4: js key in dict

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