How To Use Axios with React

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Introduction

Many projects on the web need to interface with a REST API at some stage in their development. Axios is a lightweight HTTP client based on the $http service within Angular.js v1.x and is similar to the native JavaScript Fetch API.

Axios is promise-based, which gives you the ability to take advantage of JavaScript’s async and await for more readable asynchronous code.

You can also intercept and cancel requests, and there’s built-in client-side protection against cross-site request forgery.

In this article, you will see examples of how to use Axios to access the popular JSON Placeholder API within a React application.

Prerequisites

To follow along with this article, you’ll need the following:

Step 1 — Adding Axios to the Project

In this section, you will add Axios to the digital-ocean-tutorial React project you created following the How to Set up a React Project with Create React App tutorial.

To add Axios to the project, open your terminal and change directories into your project:

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cd digital-ocean-tutorial

Then run this command to install Axios:

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npm install axios

Next, you will need to import Axios into the file you want to use it in.

Step 2 — Making a GET Request

In this example, you create a new component and import Axios into it to send a GET request.

Inside the src folder of your React project, create a new component named PersonList.js:

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nano src/PersonList.js

Add the following code to the component:

digital-ocean-tutorial/src/PersonList.js

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import React from 'react';
import axios from 'axios';

export default class PersonList extends React.Component {
  state = {
    persons: []
  }

  componentDidMount() {
    axios.get(`https://jsonplaceholder.typicode.com/users`)
      .then(res => {
        const persons = res.data;
        this.setState({ persons });
      })
  }

  render() {
    return (
      <ul>
        { this.state.persons.map(person => <li>{person.name}</li>)}
      </ul>
    )
  }
}

First, you import React and Axios so that both can be used in the component. Then you hook into the componentDidMount lifecycle hook and perform a GET request.

You use axios.get(url) with a URL from an API endpoint to get a promise which returns a response object. Inside the response object, there is data that is then assigned the value of person.

You can also get other information about the request, such as the status code under res.status or more information inside of res.request.

Step 3 — Making a POST Request

In this step, you will use Axios with another HTTP request method called POST.

Remove the previous code in PersonList and add the following to create a form that allows for user input and subsequently POSTs the content to an API:

digital-ocean-tutorial/src/PersonList.js

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import React from 'react';
import axios from 'axios';

export default class PersonList extends React.Component {
  state = {
    name: '',
  }

  handleChange = event => {
    this.setState({ name: event.target.value });
  }

  handleSubmit = event => {
    event.preventDefault();

    const user = {
      name: this.state.name
    };

    axios.post(`https://jsonplaceholder.typicode.com/users`, { user })
      .then(res => {
        console.log(res);
        console.log(res.data);
      })
  }

  render() {
    return (
      <div>
        <form onSubmit={this.handleSubmit}>
          <label>
            Person Name:
            <input type="text" name="name" onChange={this.handleChange} />
          </label>
          <button type="submit">Add</button>
        </form>
      </div>
    )
  }
}

Inside the handleSubmit function, you prevent the default action of the form. Then update the state to the user input.

Using POST gives you the same response object with information that you can use inside of a then call.

To complete the POST request, you first capture the user input. Then you add the input along with the POST request, which will give you a response. You can then console.log the response, which should show the user input in the form.

Step 4 — Making a DELETE Request

In this example, you will see how to delete items from an API using axios.delete and passing a URL as a parameter.

Change the code for the form from the POST example to delete a user instead of adding a new one:

digital-ocean-tutorial/src/PersonList.js

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import React from 'react';
import axios from 'axios';

export default class PersonList extends React.Component {
  state = {
    id: '',
  }

  handleChange = event => {
    this.setState({ id: event.target.value });
  }

  handleSubmit = event => {
    event.preventDefault();

    axios.delete(`https://jsonplaceholder.typicode.com/users/${this.state.id}`)
      .then(res => {
        console.log(res);
        console.log(res.data);
      })
  }

  render() {
    return (
      <div>
        <form onSubmit={this.handleSubmit}>
          <label>
            Person ID:
            <input type="text" name="id" onChange={this.handleChange} />
          </label>
          <button type="submit">Delete</button>
        </form>
      </div>
    )
  }
}

Again, the res object provides you with information about the request. You can then console.log that information again after the form is submitted.

Step 5 — Using a Base Instance in Axios

In this example, you will see how you can set up a base instance in which you can define a URL and any other configuration elements.

Create a separate file named api.js:

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nano src/api.js

Export a new axios instance with these defaults:

digital-ocean-tutorial/src/api.js

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import axios from 'axios';

export default axios.create({
  baseURL: `http://jsonplaceholder.typicode.com/`
});

Once the default instance is set up, it can then be used inside of the PersonList component. You import the new instance like this:

digital-ocean-tutorial/src/PersonList.js

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import React from 'react';
import axios from 'axios';

import API from '../api';

export default class PersonList extends React.Component {
  handleSubmit = event => {
    event.preventDefault();

    API.delete(`users/${this.state.id}`)
      .then(res => {
        console.log(res);
        console.log(res.data);
      })
  }
}

Because http://jsonplaceholder.typicode.com/ is now the base URL, you no longer need to type out the whole URL each time you want to hit a different endpoint on the API.

Step 6 — Using async and await

In this example, you will see how you can use async and await to work with promises.

The await keyword resolves the promise and returns the value. The value can then be assigned to a variable.

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handleSubmit = async event => {
  event.preventDefault();

  //
  const response = await API.delete(`users/${this.state.id}`);

  console.log(response);
  console.log(response.data);
};

In this code sample, the .then() is replaced. The promise is resolved, and the value is stored inside the response variable.

Conclusion

In this tutorial, you explored several examples on how to use Axios inside a React application to create HTTP requests and handle responses.

原文链接：https://www.digitalocean.com/community/tutorials/react-axios-react