Solutions for the TypeError: map.get is not a function in JavaScript

Posted on by Tom Joseph
TypeError: map.get is not a function in JavaScript

To easily solve the TypeError: map.get is not a function in JavaScript, we must first see why the error is appearing. After carefully reading the causes in the article, let’s see how we solve them.

Why does the TypeError: map.get is not a function in JavaScript occur?

To understand how the error appears, follow the example below.

Example

const map = {};
console.log(map.get("name"));

Output

Uncaught TypeError: map.get is not a function

The root cause is using the get method on an object that is not a Map object.

How to fix this error?

After figuring out the cause, we figured out how to fix it:

  • Use the constructor property
  • Use the Object.entries() method
  • Use the instanceof operator

Use the constructor property

This property will return a reference to the object constructor, the object constructor that creates the instance of an object.

Let’s see how we solve it with the example below.

Example

const map = new Map([["name", "LearnShareIT"]]);

// Check whether the constructor is a Map constructor or not
if (map.constructor === Map) {
	console.log(map.get("name"));
} else {
	console.log("Error");
}

Output:

LearnShareIT

We solve problems based on their cause.

To avoid “TypeError: map.get is not a function” in JavaScript, you must ensure that the object you use for the get() method is a Map object. We check if the object constructor is a Map constructor using the ‘constructor’ property. If it is a Map constructor, we allow access to the get() method to get the value.

Use the Object.entries() method

This method will return an array with [key, value] pairs.

Syntax:

Object.entries(obj)

Parameter:

  • obj: An object

Example:

// Create an object
const object = {
	name: "LearnshareIT",
};

// Convert an object to a Map object
const newMap = new Map(Object.entries(object));
console.log("name: ", newMap.get("name"));

Output

name:  LearnshareIT

If you need to convert an object to a Map object, then we use the Object.entries() method to convert the object to an array with [key, value] pairs, then take this array as a parameter to initialize a Map object.

Once we have a map object, we allow access to the get() method.

Use the instanceof operator

This operator checks if the constructor prototype property is present in the object’s prototype chain.

Syntax:

object instanceof constructor

Parameters:

  • object: is an object.
  • constructor: is a constructor.

Example:

// Creating a new Map
const map = new Map([["name", "LearnShareIT"]]);

// Check which constructor the object is created from
if (map instanceof Map) {
	console.log(map.get("name"));
} else {
	console.log("Error");
}

Output

LearnShareIT

We use the instanceof operator to check if an object is created from the Map constructor; if yes, we allow the get() method; otherwise, we output to the console as the string “Error”.

Summary

In this article, we have shown you some ways to fix the TypeError: map.get is not a function in JavaScript. Please look at the article carefully to apply these methods to your problem. Our site has a lot of great articles like this; follow us to learn many valuable things. Have a nice day!

Maybe you are interested:

Related Posts

Leave a Reply

Your email address will not be published. Required fields are marked *