think-await

think-await

think-await runs a time-consuming operation. The operation may be called several times concurrently, but within think-await, it will only be run once before it's finished.

In particular, You can use think-await to avoid duplicate requests for a remote API.

Syntax

import thinkAwait from 'think-await';
thinkAwait(key, callback)

• key {String} the identity of the operation.
• callback {Function} the function which contains the operation and returns a Promise object.
• return {Object} a Promise object.

Usage

Take reading a local file for an example:

import thinkAwait from 'think-await';
import fs from 'fs';

let readTimes = 0;
let awaitKey = 'readMyFile';
let filePath = '../my/file/path';
let readMyFileCallback = () => {
  return new Promise((resolve, reject) => {
    // even if `readMyFile` operation is called several times,
    // `readMyFileCallback` will only be run once before it's finished.
    readTimes ++;
    fs.readFile(filePath, {encoding: 'utf8'}, (err, data) => {
      if(err) reject(err);
      resolve(data);
    });
  });
}

let promise1 = thinkAwait(awaitKey, readMyFileCallback);
let promise2 = thinkAwait(awaitKey, readMyFileCallback);

return Promise.all([promise1, promise2]).then(values => {
  console.log(readTimes); // 1
});