Using Object.keys() in JavaScript

Object.keys(obj) returns the name property of the object which becomes handy to enumerate the property names, in the same order as returned with a normal loop.

     Input:

const myObject = {  name: 'somename',  age: 40,  gender: 'female'};

console.log(Object.keys(myObject));

     Output:

["name", "age", "gender"]

For non-object, the return type is an empty array.

     Input:

console.log(Object.keys(''));

     Output:

[]

For input of array type, it is the index of the array.

     Input:

console.log(Object.keys(['hello', 'hello2']));

     Output:

["0", "1"]

And for input of type string, the output is the array of the index for characters.

     Input:

console.log(Object.keys('hello2'));

     Output:

["0", "1", "2", "3", "4", "5"]

Syntax:

Object.keys(obj)

Parameter:

The object of which the enumerable's own properties are to be returned.

Return value:

An array of strings representing all the enumerable properties of the given object.

Exception:

Throws exception if parameter is not a valid object i.e.  null or undefined.

More at https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys