typed-pmfy v0.1.0

typed-pmfy

A few helpers for working with promise in typescript.

install

npm install typed-pmfy

api

pmfy

Turns node style async functions into returning promises.

Signature

function pmfy(fn: any, thisContext?: any): Promise;

// fn is a node style async function, meaning:
// 1. last parameter is callback
// 2. callback first paramter is reserved as error

Example

import * as fs from 'fs';
import {pmfy} from "typed-pmfy"
const stat = pmfy(fs.stat);
stat(__filename).then((stat)=>{ test.done() })

Caveats: a few overloaded pmfy definitions with different tmeplate paramters are exported, but they do not cover every use case. If typescript complains, simply override it. Example:

const pmfyCall = pmfy(somefunction) as (arg1: T1, arg2: T2)=>Promise<R>;

timeOut

Signature

function timeOut<T>(mswait: number, promise: Promise<T>): Promise<T> ;

Example

import {timeOut} from "typed-pmfy"
const f2 = async(): Promise<string> => {  // resolve 'a' after 50ms
  await new Promise((resolve, reject)=>setTimeout(resolve, 50));
  return 'a';
}
let w = timeOut(1, f2());  // wait for f2(), but only for 1ms, reject if timed out
w.catch((err)=>{
  console.log(err);   // timed out error here
});

race

Wrapper around Promise.race with tweaks. See Examples below.

Signature

function race(tasks: PromiseLike[], ignoreError?: boolean): Promise;

Example:

Race empty array resolves instead of hanging.

import {race} from "typed-pmfy"
race([]).then(()=>{ 
  console.log('this resolves');
})

Allow ignore error when racing, when called with 'true' as 2nd parameter.

race([Promise.reject('e'), Promise.reject('f'), Promise.resolve('x')], true).then((v)=>{ 
  console.log(v);   // v is 'x', 
}).catch((v)=>{
  console.log('never gets here');
})

If all raced Promises are rejected, how to prevent race from hanging? Use timeOut:

import {race, timeOut} from "typed-pmfy"
timeOut(1000, race(tasks, true)).then((result)=>{}).catch((timeoutError)=>{});