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:

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

    // ...

}

or:

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if ('key' in myObject) {

    // ...

}

Warnings:

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

   Copy

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   1

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

   2

       // ...

   3

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

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

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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.

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

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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.

1. JavaScript - check if object has property or function

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