JavaScript - check if object has key

In this article, we would like to show you how to check if object has certain key in JavaScript.

Quick solutions:

if (Object.prototype.hasOwnProperty.call(myObject, 'key')) {
    // ...
}

or:

if ('key' in myObject) {
    // ...
}

Warnings:

1. using myObject.hasOwnProperty() construction may lead to mistakes by function overriding.
   Incorrect code:

   if (myObject.hasOwnProperty('key')) {
       // ...
   }

2. it is more safe to use hasOwnProperty() function than in operator.

Practical examples

1. Using hasOwnProperty() method

In this example we use hasOwnProperty() method to check if user object has age property.

// ONLINE-RUNNER:browser;

const user = { id: 1, name: 'Tom', age: 25 };

if (Object.prototype.hasOwnProperty.call(user, 'name')) {
    console.log('The user object contains name property.');
}

Note:

This solution is safer than in operator.

2. Using in operator

In this example we use in operator to check if user object has age property.

// ONLINE-RUNNER:browser;

const user = { id: 1, name: 'Tom', age: 25 };

if ('name' in user) {
    console.log('The user object contains name property.');
}

Warning:

The in operator matches all object keys, including those in the object's prototype chain.

See also

1. JavaScript - check if object has property or function

References

1. in operator - JavaScript | MDN
2. Object.prototype.hasOwnProperty() - JavaScript | MDN