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Allows writing simple synchronous function an use them later as asynchronous


Allows writing simple synchronous function an use them later as asynchronous.

Sometimes, code written in syncronous style looks better, but when you need to use it as asynchronous function, you always need to check for callback presence, manage, when to return result — schedule with process.nextTick(), setImmediate, or call it directly.

make-async takes this problem away, and you can write bunch of simple synchronous functions, that return result or error as an instance of Error class. Moreover, when you wrap your synchronous functions, you can specify when callback should be called (see "When to call back" section).


npm install make-async


// Require make-async
var makeAsync = require('make-async'),

// Synchronous function to wrap
function sum(a, b) {
    return a + b;

// Wrap our synchronous function
asyncSum = makeAsync(sum);

// When we call it
asyncSum(1, 2, function (err, result) {
    // err will be null
    // result will equal to 3

Dealing with errors

If wrapped sync function returns an instance of Error, it will be passed as first argument to provided callback.

// Require make-async
var makeAsync = require('make-async'),
function errorFunc() {
    return new Error('Some error');

asyncErrorFunc = makeAsync(errorFunc);

asyncErrorFunc(function (err, result) {
    // err will be instance of Error returned from sync function
    // result will be null

When to call back

There is optional second argument to makeAsync that determines, when callback function will be actually called. Possible values are:

  • 'immediate' (default) — callback will be called using setImmediate function provided by node v0.10. If setImmediate is not defined, if will fall back to 'nextTick'.
  • 'nextTick' — callback will be called using process.nextTick()
  • 'direct' — callback will be called immediately

'this' variable

Don't rely on this variable in your functions — makeAsync calls your functions with null value as this value. Just write functions which rely only on their arguments to produce return.


Tests are written in mocha, and placed in /test folder. To run them, just call mocha in shell.

$ mocha