reso.js

reso.js is a robust, Typescript-first Node.js client designed for interacting with RESO Web API services.

It is fully compliant with the current RESO Web API specification and provides commonly used features out-of-the-box, including:

• Automatic Pagination
• Authentication
• Built-in Rate Limiting

It includes features like custom request/response hooks, automatic authentication token refresh, and built-in rate limiting.

Table of Contents

• Installation
• Compatibility
• Usage
  • Getting Started
    • Bearer Token Authentication
    • Client Credentials Authentication
  • Querying the API
    • readByQuery
    • readById
  • Fetching $metadata
  • Rate Limiting
  • Hooks
  • Error Handling
• Contributing
• License

Installation

Install with your preferred package manager:

pnpm add reso.js
# or
npm install reso.js
# or
yarn add reso.js

Compatibility

This library works with any RESO-compliant server following the RESO Web API spec. Additionally, it provides official support for:

• Spark Platform
• Trestle
• Bridge Interactive
• MLS Grid

Usage

Getting Started

reso.js supports both Bearer Token and Client Credentials authentication strategies. Refer to your feed's documentation for your the supported strategy and how to obtain credentials.

Bearer Token Authentication

This strategy is used when you have a long-lived, non-expiring token.

import { createFeed } from 'reso.js';

const feed = createFeed({
	http: {
		baseURL: 'http://my-reso-api.com',
	},
	auth: {
		type: 'token',
		credentials: {
			token: 'MY_TOKEN',
		},
	},
});

The bearer token provided must not expire.

Client Credentials Authentication

This strategy is required when the provider uses the OAuth 2.0 Client Credentials flow, it will autemtically refresh the token before it expires.

import { createFeed } from 'reso.js';

const feed = createFeed({
	http: {
		baseURL: 'http://my-reso-api.com',
	},
	auth: {
		type: 'credentials',
		credentials: {
			tokenURL: 'http://my-reso-api.com/token',
			clientId: 'MY_CLIENT_ID',
			clientSecret: 'MY_CLIENT_SECRET',
			// Optional: grantType and scope
		},
		// Optional: Custom refresh buffer (default is 30,000ms / 30 seconds)
		// refreshBuffer: 40000,
	},
});

Types Safety (Typescript)

For an enhanced development experience, you can pass a generic type to createFeed to auto type the client to your resources shapes, enabling full type-safety for all operations.

import { createFeed } from 'reso.js';

// 1. Define the TypeScript interface for your RESO resources.
// This generic type maps resource names (e.g., 'Property') to their expected shape.
interface Resources {
	Property: {
		ListingId: string;
		ListPrice: number;
		// ... all other expected properties
	};
	Agent: { Name: string };
}

// 2. Create the feed instance, applying the Resources generic.
const feed = createFeed<Resources>({
	http: {
		baseURL: 'http://my-reso-api.com',
	},
	// ... config
});

// 3. Read a specific resource by ID.
// Because the feed is typed with <Resources>, the 'Property' resource
// and the 'myProperty' response are fully type-safe, preventing runtime errors.
const myProperty = await feed.readById('Property', 123);

// This access is now guaranteed to be type-safe!
console.log(myProperty.data.ListingId);

Querying the API

readByQuery

Perform a RESO-compliant query. The function is an async generator that handles auto pagination for you. Use a for await...of loop to iterate through all pages of results.

for await (let properties of feed.readByQuery('Property', '$filter=ListPrice gt 100000')) {
	for (property of properties.data) {
		console.log(property);
	}
}

readById

Retrieve a specific record by ID:

const myProperty = await feed.readyById('Property', 123);
console.log(myProperty.data);

Fetching $metadata

Get the feed’s metadata XML:

const metadata = await feed.$metadata();
console.log(metadata); // The raw XML string

Rate Limiting

Rate limiting is built-in for supported providers. You can also customize limits:

Parameter	Type	Description
duration	number (ms)	The time window for the limit.
points	number	The maximum requests allowed within the duration.

const feed = createFeed({
	http: {
		baseURL: 'http://my-reso-api.com',
	},
	limiter: {
		duration: 30000, // 30 seconds
		points: 5, // max 5 requests per duration
	},
});

duration defines the time window in milliseconds, and points sets the maximum number of requests allowed within that window.

Hooks

Customize the client's behavior by passing an object of supported hooks (based on ofetch interceptors).

The clients behaviour can be customized with the following supported hooks:

Hook	Purpose
onRequest	Modify the request before it's sent.
onRequestError	Handle errors during the request setup.
onResponse	Inspect/Modify the response data after it's received.
onResponseError	Handle HTTP errors (e.g., 4xx, 5xx) before throwing.

Example – Appending /replication to Property requests:

hooks: {
  onRequest: [
    ({ request }) => {
      if (request.toLowerCase().includes('property')) {
        request += '/replication';
      }
    },
  ],
},

Error Handling

The client throws a custom FeedError with detailed RESO error information:

try {
	const myProperty = await feed.readById('Property', 123);
	console.log(myProperty.data);
} catch (error) {
	if (error instanceof FeedError) {
		console.log(error.details);
	}
}

Contributing

Bug reports, pull requests and feature discussions are welcome at GitHub

License

MIT License