The Object.keys() method in JavaScript is used to retrieve an array of the enumerable property names of an object. It returns an array containing the keys of the object.
Syntax:
Object.keys(obj);Parameter:
- obj: It is the object whose enumerable properties are to be returned.
Return Value:
It returns an array of strings that represent all the enumerable properties of the given object.
Object keys() Method Examples
Example 1: Enumerating Array Indices with Object.keys()
The code uses the Object.keys() method to retrieve the enumerable properties of the array ['x', 'y', 'z'] and logs them to the console. Since arrays in JavaScript are also objects, their indices are treated as properties. Therefore, the output will be ['0', '1', '2'].
// Returning enumerable properties
// of a simple array
let check = ['x', 'y', 'z'];
console.log(Object.keys(check));
Output
[ '0', '1', '2' ]
Example 2: Enumerating Array-Like Object Properties with Object.keys()
Here, an array-like object "check" has three property values { 0: 'x', 1: 'y', 2: 'z' } and the object.keys() method returns the enumerable properties of this array. The ordering of the properties is the same as that given by the object manually.
// Returning enumerable properties
// of an array like object.
let object = { 0: 'x', 1: 'y', 2: 'z' };
console.log(Object.keys(object));
Output
[ '0', '1', '2' ]
Applications
It can be used for returning enumerable properties of a simple array, an array-like object & an array-like object with random key ordering.
Exceptions
- It causes a TypeError if the argument passed is not an object.
- If an object is not passed as an argument to the method, then it persuades it and treats it as an object.
We have a complete list of JavaScript Object methods, to check those please go through this JavaScript Object Complete Reference article.