asunder

A small library useful for splitting apart callbacks by their arguments.

Supports node.js require, AMD define, or no module loader at all (in the browser).

Install

npm install asunder

Example

var a = require('asunder');
var fs = require('fs');

fs.readFile('./node_modules/asunder/asunder.js', a.split(onError, onData));

function onError(err) {
  // oh noes
}

function onData(data) {
  // oh yiss
}

// This will print 1 2 3 4 5 to the console (with newlines between)
[1,2,3,4,5].forEach(a.farg(console.log));

// This will print 0 1 2 3 4 to the console (with newlines between).
[1,2,3,4,5].forEach(a.sarg(console.log));

// This will print the entire array to the console 5 times
[1,2,3,4,5].forEach(a.targ(console.log));

Methods

asunder.split(fn1, fn2, ..., fnn)

Returns a function that splits up the passed in arguments and calls them with a given set of functions. If fewer functions are provided than arguments passed in, the last function will be called with all remaining arguments. Useful for when you want to bubble up errors without the standard if (err) return callback(err) pattern.

Example: Suppose this script is called firstword.js

var s = require('asunder').split;
var fs = require('fs');

function firstWordInFile(file, callback) {
  fs.readFile(file, {encoding: 'utf8'}, s(callback, function(data) {
    callback(null, data.split(' ').shift());
  }));
}

function log(message) {
  if (message) console.log(message);
}

firstWordInFile(process.argv[2], s(log, log));

$ node firstword.js firstword.js
> var
$ node firstword.js firstword.py
> { [Error: ENOENT, open '..firstword.py'] ... }

asunder.args(fn, start, [end], [context])

Returns a function that when called, will execute fn with arguments starting at the zero-based index of start and optionally ending at the argument index before end. Think of it like calling Array.prototype.slice on a set of arguments to pass along to fn, because really, that's all this is doing. Optionally define a context in which to call fn.

asunder.withArgs(start, [end])

A helper method to generate aliased asunder.args functions. For example, asunder.farg, asunder.sarg and asunder.targ are just asunder.withArgs(0), asunder.withArgs(1), and asunder.withArgs(2) respectively.

Example:

/* aliases for first, second, and third arguments */
asunder.farg = asunder.withArgs(0);
asunder.sarg = asunder.withArgs(1);
asunder.targ = asunder.withArgs(2);

asunder.farg(fn, [context])

Returns a function that when called, will exectute fn with the first argument passed in, ignoring all other arguments. Optionally, fn can be called with a context.

asunder.sarg(fn, [context])

The same as asunder.farg but uses the second argument passed in.

asunder.targ(fn, [context])

The same as asunder.farg but uses the third argument passed in.

License

MIT