How can I add a key/value pair to an JavaScript object?

In this article, you will learn how can I add a key/value pair to an JavaScript object. To understand this you have the basic knowledge of JavaScript Object.

Example 1 : Adding a key/value pair to an object using bracket notation

// add a key/value pair to an object

const person = {
    name: 'Ikhlaque',
    age: 29,
    gender: 'Male'
}
// add a key/value pair
person['height'] = 5.9;

console.log(person);

Example 2: Using the forEach() method to iterate through the array.

const array = [{id: 3}, {id: 2}];

array.forEach(object => {
  object.color = 'red';
});

// 👇️ [{id: 3, color: 'red'}, {id: 2, color: 'red'}]
console.log(arr);

The function that we pass to the forEach method will be called with each element in the array. With each iteration, we add a key/value pair to the current object.

Example 3: Using map function we can achieve same result as above.

const array = [{id: 3}, {id: 2}];

const arrWithColor = array.map(object => {
  return {...object, color: 'red'};
});

// 👇️ [{id: 3, color: 'red'}, {id: 2, color: 'red'}]
console.log(arrWithColor);

// 👇️ [{id: 3}, {id: 2}]
console.log(array);

The function that we pass to the Array.map method will be called with each element (object) in the array. We use the spread operator (…) to unpack each object’s key/value pairs and add an additional key/value pair.

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