Lazy Props

lazy-fetch-props is a TypeScript library that provides a way to lazily load and resolve properties in JavaScript objects. It is particularly useful when dealing with large datasets or when you need to fetch data from an API on-demand.

Installation

To install the library, use npm or yarn:

npm install lazy-fetch-props

or

yarn add lazy-fetch-props

Usage

Basic Example

Here is a basic example of how to use lazy-fetch-props to lazily load properties from an API:

import { createLazyLoaderProxy } from 'lazy-fetch-props';

const target = {
    user: {
        ref: '123',
        collection: 'users'
    }
};

const options = {
    endpoint: 'https://api.example.com',
    fetchUrl: '/api/v1/data/:collection/:ref'
};

const proxy = createLazyLoaderProxy(target, options);

(async () => {
    const user = await proxy.user;
    console.log(user); // { name: 'John Doe', ref: '123', collection: 'users', _meta: { _loaded: true } }
})();

Handling Arrays

lazy-fetch-props can also handle arrays of lazy reference objects:

import { createLazyLoaderProxy } from 'lazy-fetch-props';

const target = {
    users: [
        { ref: '123', collection: 'users' },
        { ref: '456', collection: 'users' }
    ]
};

const options = {
    endpoint: 'https://api.example.com',
    fetchUrl: '/api/v1/data/:collection/:ref'
};

const proxy = createLazyLoaderProxy(target, options);

(async () => {
    const users = await Promise.all(proxy.users);
    console.log(users);
    // [
    //     { name: 'John Doe', ref: '123', collection: 'users', _meta: { _loaded: true } },
    //     { name: 'Jane Doe', ref: '456', collection: 'users', _meta: { _loaded: true } }
    // ]
})();

Custom Fetcher

You can provide a custom fetcher function to handle the data fetching logic:

import { createLazyLoaderProxy } from 'lazy-fetch-props';

const target = {
    user: {
        ref: '123',
        collection: 'users'
    }
};

const options = {
    fetcher: async (prop) => {
        const response = await fetch(`https://api.example.com/api/v1/data/${prop.collection}/${prop.ref}`);
        return response.json();
    }
};

const proxy = createLazyLoaderProxy(target, options);

(async () => {
    const user = await proxy.user;
    console.log(user); // { name: 'John Doe', ref: '123', collection: 'users', _meta: { _loaded: true } }
})();

API

createLazyLoaderProxy(target, options)

Creates a proxy object that lazily loads properties.

• target: The target object to be proxied.
• options: An object containing the following optional properties:
  • isRefObject: A function to determine if an object is a reference object.
  • fetcher: A custom fetcher function to handle data fetching.
  • endpoint: The base URL for the API.
  • fetchUrl: The URL template for fetching data.
  • getCachedKey: A function to get the cache key for a property.
  • getCachedValue: A function to get the cached value for a key.

License

This project is licensed under the MIT License.