How To Check If A Map Is Empty In JavaScript

If you don’t know how to check if a map is empty in JavaScript, don’t worry. We will give you some solutions in this article. Read on it.

How to check if a Map is Empty in JavaScript

Map in JavaScript is a data structure storing key-value data, similar to an object. However, they differ in that:

• Object only allows using String or Symbol as key.
• The map allows any data type (String, Number, Boolean, NaN, Object,…) can be key.

To initialize an empty Map, you must pass no parameters to the constructor.

Use Map. size method

To get the number of Map elements in JavaScript, you use the Map.size method.

Syntax:

map.size

Parameter: None

Here we will create an empty Map and check if it is empty or not by comparing its length with the value 0. If true, then returns true, and if false, returns false.

Code:

function App() {
  const exampleMap = new Map()
  var check="false";

  if(exampleMap.size===0){
    check="true";
  }

  return (
    <div>
      <h2>Check if a Map is Empty in JavaScript | LearnShareIT</h2>
      <h3>Example Map is Empty : {check}</h3>
    </div>
  );
}
 
export default App;

Output:

So we can check whether any map is empty or not with a basic code. If you want to learn more ways to do it, follow the next part of the article.

Use Object.keys(Map).length method

Object. keys() is a method used to create an array with all an object’s keys. 

Syntax:

Object.keys(obj)

Parameter:

• Obj: an object whose properties are to be returned by the enumerable.

However, here we will only take a single key, the exampleMap declared above. And with the Object. Keys (Map).length method, we can get the length of the map we need to find and check if it is empty.

Code:

function App() {
  const exampleMap = new Map()
  var check="false";

  if(Object.keys(exampleMap).length===0){
    check="true";
  }

  return (
    <div>
      <h2>Check if a Map is Empty in JavaScript | LearnShareIT</h2>
      <h3>Example Map is Empty : {check}</h3>
    </div>
  );
}
 
export default App;

With this approach, we also achieve the same result as the one above, but we must be careful not to declare more than one variable with the same key as the map being checked. Hope it will help you.

Summary

To summarize, there are many answers for how to check if a map is empty in JavaScript. After reading this article, we know some simple ways, belike using Map. size method or using Object.keys(Map).length method. Let’s try these methods. They are helpful for you!

Maybe you are interested:

• How To Merge Maps In JavaScript
• Iterate over a Map in Reverse Order using JavaScript
• How to Filter a Map in JavaScript

Nathaniel Kirk

Hi, my name’s Nathaniel Kirk. I’m interested in learning and sharing knowledge about programming languages. My strengths are C, C++, Python, HTML, CSS, Javascript, and Reactjs. If you have difficulty with them, don’t worry. I’m here to support you.

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Name of the university: PTIT
Major: IT
Programming Languages: C, C++, Python, HTML, CSS, Javascript, Reactjs