JavaScript Maps
A Map holds key-value pairs where the keys can be any datatype.
A Map remembers the original insertion order of the keys.
How to Create a Map
You can create a JavaScript Map by:
- Passing an Array to
new Map() - Create a Map and use
Map.set()
The new Map() Method
You can create a Map by passing an Array to the new Map() constructor:
Example
// Create a Map
const fruits = new Map([
["apples", 500],
["bananas", 300],
["oranges", 200]
]);
Try it Yourself »
The set() Method
You can add elements to a Map with the set() method:
Example
// Create a Map
const fruits = new Map();
// Set Map Values
fruits.set("apples", 500);
fruits.set("bananas", 300);
fruits.set("oranges", 200);
Try it Yourself »
The set() method can also be used to change existing Map values:
The get() Method
The get() method gets the value of a key in a Map:
Maps are Objects
typeof returns object:
instanceof Map returns true:
JavaScript Objects vs Maps
Differences between JavaScript Objects and Maps:
| Object | Map |
|---|---|
| Not directly iterable | Directly iterable |
| Do not have a size property | Have a size property |
| Keys must be Strings (or Symbols) | Keys can be any datatype |
| Keys are not well ordered | Keys are ordered by insertion |
| Have default keys | Do not have default keys |
Complete Map Reference
For a complete reference, go to our:
Complete JavaScript Map Reference.
The reference contains descriptions and examples of all Map Properties and Methods.
Browser Support
Map is an ES6 feature (JavaScript 2015).
ES6 is fully supported in all modern browsers since June 2017:
| Chrome 51 | Edge 15 | Firefox 54 | Safari 10 | Opera 38 |
| May 2016 | Apr 2017 | Jun 2017 | Sep 2016 | Jun 2016 |
Map is not supported in Internet Explorer.
