Object.keys

Object.keys() returns an array whose elements are strings corresponding to the enumerable string-keyed property names found directly upon object. This is the same as iterating with a for…in loop, except that a for…in loop enumerates properties in the prototype chain as well. The order of the array returned by Object.keys() is the same as that provided by a for…in loop.

Object.keys() is an ECMAScript6 (ES6) feature.

Example 1:

const fruits = ["Banana", "Orange", "Apple", "Mango"];
const keys = Object.keys(fruits);

Output:

0,1,2,3

Example 2:

const fruits = "Banana";
const keys = Object.keys(fruits);

Output:

0,1,2,3,4,5

Example 3:

const person = { firstName: "John", 
lastName: "Doe", 
age: 50, 
eyeColor: "blue" }; 
const keys = Object.keys(person);

Output:

firstName,lastName,age,eyeColor