Promise pending lock

Call an async function multi before the first resolve, only run once and share the result.

install

npm install promise-pending-lock

Usage

Simple

import promisePendingLock from 'promise-pending-lock';

function task() {
  return Promise.resolve({});
}

const fn = promisePendingLock(task);
Promise.all([fn(), fn()])
  .then(([r1, r2]) => {
    console.log(r1 === r2);// true
  });

Hash param

Note: If the task function has params, you should provide the hashParams function to transform the params array to a cache key. By default, tread the params array as a string.

import promisePendingLock from 'promise-pending-lock';
import hash from 'object-hash';

function task() {
  return Promise.resolve({});
}

const fn = promisePendingLock(task, {hashParams: hash});
Promise.all([fn({foo: 'bar'}), fn({foo: 'bar'}), fn({foo: 'baz'})])
  .then(([r1, r2, r3]) => {
    console.log(r1 === r2);// true
    console.log(r1 === r3);// false
  });

Clone result

import _ from 'lodash/fp';
import promisePendingLock from 'promise-pending-lock';

function task() {
  return Promise.resolve({});
}

const fn = promisePendingLock(task, {cloneResult: _.cloneDeep});

Promise.all([fn(), fn()])
  .then(([r1, r2]) => {
    console.log(r1 === r2);// false
    console.log(_.equals(r1, r2));// true
  });

Integration with TypeScript

promise-pending-lock includes TypeScript definitions.

import promisePendingLock from 'promise-pending-lock';

Use dtslint to check the definition file.

npm run dtslint