Javascript check if object has property

The best way of checking if a key exists in an object is to use the hasOwnProperty() method.

Copy
let person = {name: 'John', age: 30, address: '18/1, Dover lane' };
console.log(person.hasOwnProperty('address'));

This property returns true or false based upon the presence of that property.

Another way is to directly check the property by trying to access it.

For example:

Copy
let person = {name: 'John', age: 30, address: '18/1, Dover lane' };
if (person.address) {
.......
// Your logic goes here
.......
}

Or like this:

Copy
if (person['address']) {
.......
// Your logic goes here
.......
}

The only drawback of the latter method is that we can’t be sure if the object property doesn’t exist or its value is set to null or undefined or false.