REST API client

The REST API client utility module provided by Peregrine allows you to work with non-GraphQL web APIs. The default implementation is a client that works with the REST API for Magento 2.3 and above.

Magento 2 REST API client

The Magento 2 REST API client provides a request() function which places a request to a Magento backend and returns a Promise as a response. This function is similar to the Web standard fetch() function with a few differences in response and error handling. It also contains features to support multicasting and rolling requests.

For basic use cases, use the request() method. For more advanced cases, use the M2ApiRequest class, which the request() method wraps.


request(resourceUrl, opts)


resourceUrl (UVString)

A Magento REST endpoint.

opts (object)

An options object that can contain all possible fetch options.

Additional options:

  • parseJSON (boolean): Automatically parse the response into JSON format. Defaults to true.
  • multicast (boolean): Manually set whether a request should use the multicasting feature.


A Promise object that contains the result of the request. See response handling.


The following example imports the request() function into another module:

import { RestApi } from '@magento/peregrine';

const { request } = RestApi.Magento2;

Use the request() function to place and receive API calls using async/await syntax:

async function displayGuestCartItems(cartId) {
    const cartResponse = await request(
            method: 'GET'
    const cart = await cartResponse;

Or use the Promise object directly:

function displayGuestCartItems(cartId) {
    return request(
            method: 'GET'
    .then(({ items }) => console.log(items);)

Response handling

The request() method returns a Promise object with a fully parsed REST resource instead of an HTTP response as in the standard fetch() API.

To make request() behave like fetch(), set the value of parseJSON to false in the options object. This changes the value passed to the Promise.resolve() function back to a Response object.

        method: 'GET',
        parseJSON: false
).then(({ response }) => console.log(response);)

Error handling

Promises returned by request() are rejected if the server responds with an HTTP error code within the 4xx-5xx range. This is different from the standard fetch() behavior, which ignores HTTP errors so it can resolve the promise and only fails on network connectivity errors.

The Magento REST API uses HTTP error codes to denote failed operations, so the request() method responds to these server-side errors by rejecting them. When the server returns an error code, the request() method builds an error containing metadata for debugging and rejects the Promise.


The multicasting feature of the Magento 2 REST client collects all successive calls to the request() method and returns a single request and response that is shared to all method callers.

In any distributed architecture, where applications are built from components with view, behavior, and data fetching strategy, multiple components may request the same resource at the same time. GraphQL clients resolve this by merging GraphQL queries together, dispatching a request as a single call, and distributing the pieces of the GraphQL response to the original callers. A direct call using fetch() or XMLHttpRequest() does not provide this functionality.

The request() method makes up for this by using a pattern-matching rule on inflight requests. All requests with the same method, path, and body text are considered multicastable by default. A clone of the response object is returned if a request meets the following criteria:

  • The pattern of the new request matches one that is already in progress, i.e. the network has not loaded the resource yet.
  • No unsafe operations, such as POST, have occurred to the target resource between the time of the original request and the new request.
  • The request is not a POST request. These requests create and/or modify server state, so it is unsafe to reuse their results.

Override multicast

The multicast configuration option forces multicasting to be true or false and bypasses the previously described rules.

// A normally multicast request forced not to multicast
request('carts/mine',{ method: 'GET', multicast: false });

// A normally non-multicast request forced to multicast
        method: 'POST',
        body: cartItem,
        multicast: true

Rolling requests

A rolling request is a multicast which overrides and replaces matching, previous multicast requests. It helps maintain a fresh resource, such as a shopping cart, and reduces network traffic by aborting outstanding matching requests.

This feature has no effect on non-multicast requests.

To use a rolling request, set the cache configuration option to reload or no-store.

The M2ApiRequest class

The request() method is a convenience wrapper on top of the M2ApiRequest class.

Use the M2ApiRequest class if you want more control over your REST requests.

import { RestApi } from '@magento/peregrine';
const { M2ApiRequest } = RestApi;

function placeCancelable(emitter) {
    const req = new M2ApiRequest(
            method: 'GET',
    emitter.on('someevent', () => {
    return req.getResponse(); // AbortError


new M2ApiRequest(resourceUrl, opts)

Creates a new M2ApiRequest class to a specific resourceUrl using the configuration values in opts. See request() method parameters.


Execute the request. This must be run before getResponse() or abortRequest() can be called.


Get the promise for the network operation. This method can only be called after run() executes. This method exists so that requests can reuse the promises from other requests.

Returns: Promise - Promise object for the result of the request.


Abort the network operation. Multicasted requests will catch the AbortError and attempt to reuse a cached request. Other requests will pass the AbortError rejection to the consumer.

Kind: Instance method of M2ApiRequest


Used to determine if a request intends to use the rolling requests feature and override prior requests to the same resource.

Returns: boolean - True if the request is rolling. False otherwise.