Object.keys() Method – Copy an Object's Keys into an Array

Whenever you use Object.keys() on a JavaScript object, the method does the following:

• It creates a new array.
• It copies the specified object’s enumerable own keys into the newly created array.
• It returns the new array containing string items representing the given object’s keys.

Syntax of the Object.keys() Method

Object.keys() accepts a single argument. Here’s the syntax:

Object.keys(objectArgument);

The objectArgument refers to the JavaScript object whose keys (property names) you want to extract into a new array.

Note

The Object.keys() method does not alter the original object.

Examples of the Object.keys() Method

Below are examples of the Object.keys() method.

Copy an object’s keys into a new array

const profile = {
  firstName: "Oluwatobi",
  lastName: "Sofela",
  companyName: "CodeSweetly",
  npmPackage: "@codesweetly/react-youtube-playlist",
};

const formFieilds = Object.keys(profile);

console.log(formFieilds);

// The invocation above will return:
// ["firstName", "lastName", "companyName", "npmPackage", "id"]

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Copy an array’s keys into a new array

const myBio = ["Oluwatobi", "Sofela", "CodeSweetly", 9103];

const keysInMyBio = Object.keys(myBio);

console.log(keysInMyBio);

// The invocation above will return:
// ["0", "1", "2", "3"]

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Copy a string’s keys into a new array

const firstName = "Oluwatobi";

const keysInFirstName = Object.keys(firstName);

console.log(keysInFirstName);

// The invocation above will return:
// ["0", "1", "2", "3", "4", "5", "6", "7", "8"]

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The Object.keys() method successfully extracted the string’s keys because strings are the only primitive data with enumerable own properties.

Tip

• Use Object.values() to extract an object’s values.
• Use Object.entries() to extract an object’s key-value pairs.