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Better Curry

Because return function(){ return fn.apply(context,; } isn't good enough, that's why better curry.

Forget Function.bind and func.apply(context, arguments), performance matters! For a better curry!

You won't find any other curry module that can achieve those benchmarks.


~ npm install better-curry


~ bower install better-curry

Works on the browser or on node.js (super duper performance on the latter)


BetterCurry.wrap(fn [, context[, len [, checkArguments]]])

When the function have all arguments defined. You can bind the new resulting function to a new context (change the this inside the function).

function base(argument1, argument2){
    return + ' ' + argument1 + argument2;
var based = BetterCurry.wrap(base, {data: 'hurry'});
based('up','!'); // 'hurry up!' 

If the function doesn't have defined parameters, you can still coerce the function to adopt a length

function base(){
    return' + ');
var based = BetterCurry.wrap(base, null, 3);
based('one', 'two', 'three', 'will be ignored'); // 'one + two + three' 

Passing a len of -1 will make sure it behaves like variadic (that is, uses fn.apply(context,;

When passing true to checkArguments, it will check if the body of the function has the arguments keyword. If so, it will use a variadic function instead of a defined length.

function base(){
    return' + ');
var based = BetterCurry.wrap(base, null, -1);
based('one', 'two', 'three', 'wont be ignored','its','free for all'); // 'one + two + three + wont be ignored + its + free for all' 

Generated function will have a __length property, that equals to the original fn length.

You may hint the function by appending the expected length to your function (or if it's already wrapped):

var myfunc = function(arg1, arg2, arg3, arg4){
myfunc.__length = 3;
BetterCurry.wrap(myfunc, null, true); // creates a threeArgs wrapped function 

BetterCurry.predefine(fn, args [, context[, len [, checkArguments]]])

Predefine creates a function that, when executed, will have the predefined arguments plus any arguments that you pass:

function base(argument){
  return argument;
var based = BetterCurry.predefine(base, ['argument','will be ignored']);
based('this will be ignored as well'); // 'argument' 

Variadic work as well, just remember to pass the len -1 (or 8 if you think it will be that big...)

function base(){
return' + ');
var curried = BetterCurry.predefine(base, ['1','2','3','4'], null, -1);
curried('5'); // '1 + 2 + 3 + 4 + 5' 
curried = BetterCurry.predefine(base, ['1','2','3','4'], null, 5);
curried('5','6'); // '1 + 2 + 3 + 4 + 5' 

All -1 len are slower since it uses Function.apply (many times slower than

When passing true to checkArguments, it will check if the body of the function has the arguments keyword. If so, it will use a variadic function instead of a defined length.

Generated function will have a __length property, that equals to the original fn length

BetterCurry.delegate(proto, target)

A minor rewrite of visionmedia's delegates but around 13% faster

var obj = {
  request: {
    _value: 1,
    function1: function(){},
    get value(){
      return this._value;
    set value(val){
      this._value = val;
var delegated = BetterCurry.delegate(obj, 'request'); //all mirror functions from obj will reflect to obj.request with the same context 
.access({name: 'value', as: 'value2'})
.method({name: 'function1', as: 'function2', args:['arg1']});
//obj is now: 
obj = {
  function1: function1(){/*...*/},
  function2: function1(arg1){/*...*/},
  value: /*..value..*/
  value2: /*..value..*/
  request: {/*...*/}


Flattens all array-like arguments passed (Array and arguments) and append them in order:

function stuff(){
    return BetterCurry.flatten([1,2,[3]], arguments);
stuff(1,2,3, [1,2,3]); // returns [1,2,[3],1,2,3,[1,2,3]] 


Just regular stuff (100% coverage by the way)

npm run test
npm run coverage
=============================== Coverage summary ===============================
Statements   : 100% ( 138/138 ), 3 ignored
Branches     : 100% ( 330/330 ), 5 ignored
Functions    : 100% ( 30/30 )
Lines        : 100% ( 138/138 )


Curious about performance? Get flabbergasted.

npm run benchmark


The MIT License (MIT)
Copyright (c) 2014 Paulo Cesar
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.