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How to add key/value pair in JavaScript object dynamically

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Using bracket notation or the defineProperty() method you can add key/value pair in JavaScript object dynamically.

JavaScript Object defineProperty() method adds or modifies an existing property on an object and returns the object. The defineProperty() method, being a static method, is called using the Object class name.

Add key/value pair in JavaScript object dynamically

Simple example code adds a new key to the existing object.

<!DOCTYPE html>
   const obj = {
    'msg': 'Hello',
  const key = "Code"

  obj[key] = "Up"




How to add key value pair in JavaScript object dynamically

Using Object.defineProperty() method

   const getId = () => {
    //API call and other stuff
    return "ID"

  const objA = {
    codez: 'up',
    test: '123',

  const key3 = getId()

  Object.defineProperty(objA, key3, 
    value: 'Nothing',
    writable: true,
    enumerable: true,
    configurable: true



Object { codez: "up", test: "123" }
Object { codez: "up", test: "123", ID: "Nothing" }

Do comment if you have any doubts or suggestions on this Js object topic.

Note: The All JS Examples codes are tested on the Firefox browser and the Chrome browser.

OS: Windows 10

Code: HTML 5 Version

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