Get JavaScript Objects from a JSON File



Introduction

JSON stands for JavaScript Object Notation.JSON is a lightweight format for storing and transporting data.JSON is often used when data is sent from a server to a web page.JSON is “self-describing” and easy to understand. JavaScript objects are an integral part of the React app, so they need to get accessed from JSON files/data to be uses in components.

This blog will demonstrate how to get a JavaScript object from a JSON file or access it using a fetch() HTTP request.



Rendering Values from a JSON File

Create one sample JSON file as given below, and save it as data.json


"employees":
"employee1": "firstName":"John", "lastName":"Doe",
"employee2": "firstName":"Anna", "lastName":"Smith",
"employee3": "firstName":"Peter", "lastName":"Jones"


Now, if you want to render any of the key-value pairs from the JSON, the .map() function would be useful to iterate the objects; the example is below.

import React,  Component  from "react";
// Import local JSON file
import Data from "./data";

export class Sample extends Component 
  render() 
    return (
      <>
        <div>
          <h3>Using local JSON file</h3>
          Object.keys(Data.employees).map((item, i) => (
            <li key=i>
              <span>Key name : item</span>
            </li>
          ))
        </div>
      </>
    );
  


export default Sample;

In the above example, to use the local JSON file needs to be consumed using the import statement.

import Data from "./data";

After that, you can access all the JSON data using Data in your component by using Object.keys() along with the .map() function.

Object.keys(Data.employees).map((item, i) => ())

Using a local JSON file in the React app is a common approach when you want to render some static data, maintain server config, etc.



Rendering JSON Objects from an API Call

You have seen the example where a local JSON file is used, but at the same time you may need to access JSON data from the server.

Implement the API call as demonstrated below.

componentDidMount() 
    fetch("https://jsonplaceholder.typicode.com/users")
      .then(res => res.json())
      .then(
        result => 
          this.setState(
            data: result
          );
        ,
        error => 
          console.log(error);
        
      );

After implementing the API call, you can access the JSON data for the rendering as below.

render() 
    return (
      <>
        <div>
          <h3>Using API call</h3>
          this.state.data &&
            this.state.data.length > 0 &&
            this.state.data.map((item, i) => (
              <li key=i>
                <span>Email : item.email</span>
              </li>
            ))
        </div>
      </>
    );

Along with the state this.state.data, the additional function used is .map(), which iterates the array items from the state and renders them into the DOM.

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Happy Reading!!!


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