Map vs Object in JavaScript

by

According to MDN:

A Map object can iterate its elements in insertion order – a for..of loop will return an array of [key, value] for each iteration.

and

Objects are similar to Maps in that both let you set keys to values,
retrieve those values, delete keys, and detect whether something is
stored at a key. Because of this, Objects have been used as Maps
historically; however, there are important differences between Objects
and Maps that make using a Map better.

An Object has a prototype, so there are default keys in the map.
However, this can be bypassed using map = Object.create(null). The
keys of an Object are Strings, where they can be any value for a Map.
You can get the size of a Map easily while you have to manually keep
track of size for an Object.

Map

The iterability-in-order is a feature that has long been wanted by developers, in part because it ensures the same performance in all browsers. So to me that’s a big one.

The myMap.has(key) method will be especially handy, and also the myMap.size property.

More Related Contents:

  1. How do you JSON.stringify an ES6 Map?
  2. How do I persist a ES6 Map in localstorage (or elsewhere)?
  3. Using Array objects as key for ES6 Map
  4. How to reliably check an object is an EcmaScript 6 Map/Set?
  5. Define a custom hash() method for use with ES6 maps
  6. JavaScript – Map() increment value
  7. map function not working in React
  8. First item from a Map on JavaScript ES2015
  9. What does “this” refer to in arrow functions in ES6?
  10. How do I write a named arrow function in ES2015?
  11. ES6: call class constructor without new keyword
  12. How can I conditionally import an ES6 module?
  13. ES2015 import doesn’t work (even at top-level) in Firefox
  14. Getting Unexpected Token Export
  15. Deep copy in ES6 using the spread syntax
  16. How to create an instance of a subclass from the super class?
  17. How can I construct a Template String from a regular string? [duplicate]
  18. Do __proto__ and Object.getPrototype of expose exactly the same functionality?
  19. Why es6 react component works only with “export default”?
  20. How to publish a module written in ES6 to NPM?
  21. What is the defined execution order of ES6 imports?
  22. Why does the Promise constructor require a function that calls ‘resolve’ when complete, but ‘then’ does not – it returns a value instead?
  23. Get the description of a ES6 Symbol
  24. How to create an array of objects from multiple arrays
  25. How should I import the Spatial Illusions milsymbol library into my webpage?
  26. Why is `throw` invalid in an ES6 arrow function?
  27. Where argument of first next() call goes? [duplicate]
  28. Why does .then() chained to Promise.resolve() allow const declaration to be reassigned?
  29. Javascript – Template Strings Don’t Pretty Print Objects
  30. How to bind methods when destructuring an object in JavaScript?

Leave a Comment