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!
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My name is Tom Joseph, and I work as a software engineer. I enjoy programming and passing on my experience. C, C++, JAVA, and Python are my strong programming languages that I can share with everyone. In addition, I have also developed projects using Javascript, html, css.
Job: Developer
Name of the university: UTC
Programming Languages: C, C++, Javascript, JAVA, python, html, css