pmfy

pmfy

Turns an async nodejs function into a ES6 Promise using terse ES6 syntax.

The function should:

• Have callback as last parameter
• Callback takes (err, ...results) as parameters

Examples

Promisify a context free function:

const pmfy = require('pmfy');
const stat = pmfy(fs.stat);
stat("file").then( (fstat)=> ... );

Promisify a function with 'this':

const pmfy = require('pmfy');
const fn = pmfy(myobj.mymethod, myobj);
fn("file", 1).then( ()=> ... );

Use it with "co" module for async looping:

const pmfy = require('pmfy');
const co = require("co");
const stat = pmfy(fs.stat);
co(function* statFiles() {
  for (const file of ['file1', 'file2']) {
    console.log(yield stat(file));  // prints out stat object
  }
}).then(()=>..);

You can also promisify an entire package, example:

const pmfy = require('pmfy');
const fse = pmfy(require('fs-extra'));

fse.emptyDir('./dir').then(...);

When promisifying a package, it's assumed that all functions with name not ending in 'Sync' are async functions.

Often it's useful to add a timeout to wait for async callback, for example when wait for network reply.
Then you can do:

const timedOutWait = pmfyAuto.timeOut(100, waitForData);
timedOutWait().catch((err)=>{   // err is an Error object with time out message, if 100ms elapsed before cb

}).then(()=>{});

A test example:

let future = require("phuture");

const waitForMax100ms = pmfyAuto.timeOut(100, future.once);

waitForMax100ms(200).catch((err)=>{
  console.log(err); // should timeout since 100<200
}).then(()=>{
})