Convert an Object to a Map in JavaScript

Convert an Object to a Map in JavaScript #

To convert an object to a Map, call the Object.entries() method to get an array of key-value pairs and pass the result to the Map() constructor, e.g. const map = new Map(Object.entries(obj)). The new Map will contain all of the object's key-value pairs.

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const obj = {
  id: 1,
  name: 'Fred',
};

// ✅ Convert Object to Map
const map1 = new Map(Object.entries(obj));
console.log(map1); // 👉️ {'id' => 1, 'name' => 'Fred'}

// ✅ Convert Map to Object
const objAgain = Object.fromEntries(map1);
console.log(objAgain); // 👉️ {id: 1, name: 'Fred'}

We used the Object.entries method to get an array of key-value pairs.

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// 👇️ [['id', 1], ['name', 'Fred']]
console.log(Object.entries({id: 1, name: 'Fred'}));

The first element in each nested array is the key and the second is the value.

We then passed the result to the Map() constructor.

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const obj = {
  id: 1,
  name: 'Fred',
};

const map1 = new Map(Object.entries(obj));
console.log(map1); // 👉️ {'id' => 1, 'name' => 'Fred'}

If you need to convert the Map back to an object, use the Object.fromEntries method.

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// 👇️ {id: 1, name: 'Fred'}
console.log(
  Object.fromEntries([
    ['id', 1],
    ['name', 'Fred'],
  ]),
);

The Object.fromEntries() method takes an iterable, such as a Map or an array as a parameter and transforms it to an object. The iterable must contain key-value pairs.

Further Reading #

• Convert a Set to a String in JavaScript
• Convert a Map to an Object in JavaScript