JavaScript - check if key exists in object

In this article, we would like to show you how to check if key exists in object working with JavaScript.

Quick solution:

// ONLINE-RUNNER:browser;

var object = { keyName: 'A'};

console.log('keyName' in object);  // true

Practical example

In this example, we use for...in statement to check if a key exists in the object. This way true value is returned even when the key value is undefined.

// ONLINE-RUNNER:browser;

var object = { keyName1: 'A', keyName2: undefined };

console.log('keyName1' in object); // true
console.log('keyName2' in object); // true (key exists but value is undefined)

console.log('keyName3' in object); // false

Alternative solution

You can also use hasOwnProperty() method to achieve the same result as above.

// ONLINE-RUNNER:browser;

var object = { keyName1: 'A', keyName2: undefined };

console.log(object.hasOwnProperty('keyName1')); // true
console.log(object.hasOwnProperty('keyName2')); // true

console.log(object.hasOwnProperty('keyName3')); // false

See also

1. JavaScript - for...in statement

References

1. for...in - JavaScript | MDN