https://github.com/profusion/lazy-load-obj

TypeScript utility to lazy load object properties when they are accessed
https://github.com/profusion/lazy-load-obj

Last synced: about 1 month ago
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TypeScript utility to lazy load object properties when they are accessed

• Host: GitHub
• URL: https://github.com/profusion/lazy-load-obj
• Owner: profusion
• Created: 2020-03-05T19:40:41.000Z (almost 5 years ago)
• Default Branch: master
• Last Pushed: 2023-01-07T15:36:59.000Z (almost 2 years ago)
• Last Synced: 2024-11-07T01:02:58.424Z (about 2 months ago)
• Language: TypeScript
• Size: 1.5 MB
• Stars: 0
• Watchers: 22
• Forks: 0
• Open Issues: 15
• Metadata Files:
  • Readme: README.md

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README

        
# Lazy Load Object Fields

Simple [Proxy](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy)

that coordinates loading fields of an object on demand.

This is useful to be matched with GraphQL, where one can return a

shallow object (ie: `{ id }`) and let the properties be loaded in one

go once used.

## Example

See [examples/](./examples/).

```typescript

/* eslint-disable no-console */

/* eslint-disable import/no-extraneous-dependencies */

import process from 'process';

import fetch from 'node-fetch';

import lazyLoadObj from '../lib';

const baseUrl = 'https://jsonplaceholder.typicode.com/';

type Todo = {

  completed: boolean;

  id: number;

  title: string;

};

const lazyTodo = lazyLoadObj(

  { id: Number(process.argv[2] || 1) },

  async (

    { id }: Partial,

    properties: readonly (keyof Todo)[],

  ): Promise> => {

    console.log(`loading todos/${id} properties`, properties);

    const response = await fetch(`${baseUrl}todos/${id}`);

    return response.json();

  },

);

const { title } = lazyTodo;

console.log('accessing title results in', title);

if (title instanceof Promise) {

  console.log('wait title promise...');

  title.then(

    value => {

      console.log('fetched title', value);

      // the next access will always return a value, since it's cached:

      console.log('access cached title', lazyTodo.title);

    },

    error => console.error('failed to fetch title', error),

  );

}

```