Wraps synchronous functions with a callback-style API

  • cbify

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1.0.010 years ago10 years agoMinified + gzip package size for cbify in KB


Wraps synchronous functions with a callback-style API so they can match their async brethren.
Useful for handling both sync and async methods with the same underlying code. Preserves the sync-ness of the original function, making it possible to use values passed to the callback as a return value.


npm install --save cbify

bower install --save cbify
The browser build for bower includes a UMD wrapper which adapts to various module systems, or exposes a cbify global if none are present.
var cbify = require('es128/cbify')


var cbify = require('cbify');

var sum = cbify(function (a, b) {
	return a + b;

var answer;
sum(32, 96, function (err, result) {
	answer = result;

console.log(answer); // 128
// would have been undefined if `sum` had handled the callback asynchronously

If provided a function whose last named argument is cb or callback (or even if it just contains callback), then that function will be returned unchanged.
The this context the cbify'd function is called with will be preserved for the underlying function. Feel free to use bind, apply, etc as you would have before implementing cbify.

Similar modules

I was surprised I couldn't find a pre-existing module that did this. I did find a few that almost did it, but were ruled out for slight differences.
Uses setImmediate, causing the wrapped function to always return asynchronously, even though the underlying method may still be blocking. The callbackify method provided by this module is only different in that it wraps the function with a continuation-style API, meaning that err will now always be the first argument. Another API style. Expects the callback at the time the function is being wrapped so the resulting function signature stays the same.

What about Z͡alg̨ó?

This makes synchronous functions pass their result to a callback synchronously. It's an important feature of this module, providing the ability to adapt some async APIs to also provide a sync option with minimal code changes. This is done knowingly and is consistent, so it does not release Zalgo.
However, you do have to be careful for ͟h͞e͘ ̢Wa͜it̛s̨ ͡B̨e͡h̛in̨d ͠The̷ W͏a͝l͏ĺ. If you do not know whether the functions you're passing into cbify are sync or async, and you are otherwise treating them identically, then you may be ́un͘l͜͝e҉a͟҉̨sh̕i̶͜҉n͏̧̕g̢̕ ̧T̷͞ḩe͟ ͜N̢̛͢e̛͟͠z̨͟ṕ̵̨e͟͡͏r̡̀d̨i̧̧a̢͢n ̡hi҉͜v̷e͢-̡͘͘mi̵͞nd̀ ̡of̀ ͢͝cḩ̕a̶̶o̷͜s͘͞.҉͝. In that case, you may want to use sinless instead, or use cbify together with dezalgo.