lion/packages/ajax

Ajax

ajax is a small wrapper around fetch which:

• Allows globally registering request and response interceptors
• Throws on 4xx and 5xx status codes
• Prevents network request if a request interceptor returns a response
• Supports a JSON request which automatically encodes/decodes body request and response payload as JSON
• Adds accept-language header to requests based on application language
• Adds XSRF header to request if the cookie is present

How to use

Installation

npm i --save @lion/ajax

Relation to fetch

ajax delegates all requests to fetch. ajax.request and ajax.requestJson have the same function signature as window.fetch, you can use any online resource to learn more about fetch. MDN is a great start.

Example requests

GET request

import { ajax } from '@lion/ajax';

const response = await ajax.request('/api/users');
const users = await response.json();

POST request

import { ajax } from '@lion/ajax';

const response = await ajax.request('/api/users', {
  method: 'POST',
  body: JSON.stringify({ username: 'steve' }),
});
const newUser = await response.json();

JSON requests

We usually deal with JSON requests and responses. With requestJson you don't need to specifically stringify the request body or parse the response body:

GET JSON request

import { ajax } from '@lion/ajax';

const { response, body } = await ajax.requestJson('/api/users');

POST JSON request

import { ajax } from '@lion/ajax';

const { response, body } = await ajax.requestJson('/api/users', {
  method: 'POST',
  body: { username: 'steve' },
});

Error handling

Different from fetch, ajax throws when the server returns a 4xx or 5xx, returning the request and response:

import { ajax } from '@lion/ajax';

try {
  const users = await ajax.requestJson('/api/users');
} catch (error) {
  if (error.response) {
    if (error.response.status === 400) {
      // handle a specific status code, for example 400 bad request
    } else {
      console.error(error);
    }
  } else {
    // an error happened before receiving a response, ex. an incorrect request or network error
    console.error(error);
  }
}

Fetch Polyfill

For IE11 you will need a polyfill for fetch. You should add this on your top level layer, e.g. your application.

This is the polyfill we recommend. It also has a section for polyfilling AbortController