How to check if a key exists in an object in javascript
Working with objects is a common and essential task in JavaScript. One of the most frequent operations is checking if a specific key exists within an object. This article explores various ways to perform this check.
Using the 'in' Operator
The 'in' operator is one of the simplest and most straightforward methods to check if an object contains a certain key. The syntax is 'key in object'.
const object = { key: 'value' };
console.log('key' in object); // returns trueMethod hasOwnProperty
The 'hasOwnProperty' method provided by JavaScript objects allows to check if the object has a specific property or key as a direct, non-inherited property.
const object = { key: 'value' };
console.log(object.hasOwnProperty('key')); // returns trueChecking Using Undefined
Another way is to check if the value of the key is different from 'undefined'. This technique is useful when it's known that the stored values are not 'undefined'.
const object = { key: 'value' };
console.log(object['key'] !== undefined); // returns true
Jorge García
Fullstack developer