Map() Method In React JS.
Tags: beginners, react, functional, programming
Published: 2022-11-04 02:50:14

**The map() method ?** A map is a data collection type where data is stored in the form of pairs. It contains a unique key. The value stored in the map must be mapped to the key. We cannot store a duplicate pair in the map(). It is because of the uniqueness of each stored key. It is mainly used for fast searching and looking up data.

In React, the ?map? method used to traverse and display a list of similar objects of a component. A map is not the feature of React. Instead, it is the standard JavaScript function that could be called on any array. The map() method creates a new array by calling a provided function on every element in the calling array.

**How to render an array of objects with Array.map in React?**

 To render an array of objects in react with JSX we need to use Array.map() to transform the object into something react can make use of because you cannot directly render an object into React. Instead, by using Array.map() to convert each object in the array into something else, like a string or a component we can then render it.

**Here is an example of how to render data using Array.map:**

```
import React from 'react';   
import ReactDOM from 'react-dom';   
  
function NameList(props) {  
  const myLists = props.myLists;  
  const listItems = myLists.map((myList) =>  
    <li>{myList}</li>  
  );  
  return (  
    <div>  
          <h2>React Map Example</h2>  
              <ul>{listItems}</ul>  
    </div>  
  );  
}  
const myLists = ['Soccer', 'Basketball', 'Swimming'];   
ReactDOM.render(  
  <NameList myLists={myLists} />,  
  document.getElementById('app')  
);  
export default App;  
```
In React, map() can be used to generate lists.


**How do you map objects in React?**
 To map through an object's value in React: Use the Object. values() method to get an array of the object's values. Call the map() method on the array of values.

**Is map a callback function?**
The map() method calls a callback function on every element of an array and returns a new array that contains the results. The map() method takes two named arguments, the first one is required whereas the second one is optional.

**What are 3 purposes of a map?**

> Maps represent the real world on a much smaller scale

1. They help you travel from one location to another.

2. They help you organize information.

3. They help you figure out where you are and how to get where you want to go.

**What is map and its advantages?**

> Two advantages of maps: 

1. Maps are easier to use and easier to carry around.
2. They can show the earth's entire surface or just a small part and can show even a small locality in a great detail.

**What is map in JS?**
 Map is a collection of elements where each element is stored as a Key, value pair. Map object can hold both objects and primitive values as either key or value. When we iterate over the map object it returns the key, value pair in the same order as inserted.

**How do I map data from API?**

> Getting Started With API Data Mapping

1. Data Discovery.
2. Define a Default Map.
3. Map Custom Data From Each Instance.
4. Make Your “Default” A Guideline, Not a Requirement.
5. Leverage Self-Service Data Mapping Tools.

**Here is my final results of my project after Map() to render the data to the home page:**

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/h8fa9m1oolqz4uef1mwr.png)

**Conclusion:**

> Using the map() function, you can pretty much do all sorts of manipulations without mutating the original array. The non-mutation part is essential, as it does not cause any side effects by default and makes it easy to debug your code. If you want to mutate the original array, you can use the traditional for or any other type of loop, or you can use the forEach() function which will need another blog to talk about.