JavaScript Map vs Object: The Main Difference

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In this JavaScript Map vs Object article, we will simplify the confusing part. Here you can see why we are comparing Map vs Object in JavaScript and why not Map vs Array. Well, you can compare any of them, But unlike others, JavaScript Map and Object have the same use cases, So it is required to understand maps vs objects more in detail.

What is a Map in JavaScript?

JavaScript map is a built-in data structure, a data collection type in which data is stored in the form of pairs. The Map contains a unique key and a value map to that key; hence, there is no chance of storing duplicate pairs.

We can create a map using a built-in map constructor as:

const usersMap = new Map([
   [1, 'Diwakar'],
   [2, 'John']
]);
  1. The primary use cases of maps are fast searching and looking for the data. 
  2. Maps provide you with a friendly interface to access entries.
  3. In maps, the key field can be of any data type like integer, array, etc. 
  4. Maps always preserve their order of elements. 
  5. In JavaScript map is an instance of an object.
  6. To check whether the key is present on the Map, use the (key) method. e.g., usersMap.has(2) //true

Example Code:

var map = new Map([
   [1, 3],
   [8, 5]
]);

console.log(map instanceof Object);

Output:

true

What is an Object in JavaScript?

JavaScript Object is a built-in data structure that can contain many values. The Object values are written as name: value pairs. Just like a map, the Object follows the same concept but is slightly different, making the Map more effective. We can create objects in the JavaScript link below:

const usersObj = {
   1: 'Diwakar',
   2: 'John'
};
  1. In objects, key fields can only be integers, strings, and symbols, which was not the case in a map.
  2. In Objects, the order of elements is not preserved.
  3. In JavaScript, objects are not an instance of maps.
  4. To check whether the key is present in the Object, use the hasOwnProperty(key) method. e.g usersObj.hasOwnProperty(2) //true

Example Code:

var obj = new Object();

console.log(obj instanceof Map);

Output

false

JavaScript Map vs Object

The main difference between JavaScript Map vs Object is that Map preserves the original order of elements, whereas Object does not preserve. JavaScript Map can contain the key-field can be of any data type (an integer, an array, or even an object), whereas JavaScript Object can have the data type of the key-field is restricted to integer, strings, and symbols.

Conclusion

So these are some fundamental differences between maps and objects in JavaScript. Objects in JavaScript are the same as hash maps of other languages. The time complexity is constant for accessing the keys from the Map. 

Also, JavaScript Map provides a friendly interface to manage the key-value properties. So it is slightly good to have maps instead of objects, but both have their properties.

That’s it for this tutorial.

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