Functional array sorting

README.md

This is a handy helper for functional sorting of arrays based on their content.

var sortBy = function(a,b,c){c=a.slice();return c.sort(function(d,e){d=b(d),e=b(e);return(d<e?-1:d>e?1:0)})};

sortBy(['Fuchs','Diaz','Schmidt'], function(name){ return name.length })
// => ["Diaz", "Fuchs", "Schmidt"]

sortBy([1,2,3], Math.random)
// => [3,1,2]

It's an implementation of Ruby's Enumberable#sort_by functionality, see http://www.ruby-doc.org/core/classes/Enumerable.html#M001481 for more info.

A similiar implementation is available in Prototype.js, as Enumerables, see http://api.prototypejs.org/language/Enumerable/prototype/sortBy/.

annotated.js

function(
  a,                // array to sort (will not be altered)
  b,                // sorting function
  c                 // placeholder
) {
  c = a.slice();    // create a clone of the array
  return c.sort(    // sort the array with JS' built-in sort function
    function(
      d,            // left
      e             // right
    ) {
      d = b(d),     // call sorting function for left...
      e = b(e);     // ...and right values.
      return (
        d < e       // if left is less then right
        ?     
        -1          // return -1
        :           // otherwise
        d > e       // if left is greater than right
        ?         
        1           // return 1
        : 
        0           // if it's the same, return 0
      )
    }
  )
}

index.js

function(a,b,c){c=a.slice();return c.sort(function(d,e){d=b(d),e=b(e);return(d<e?-1:d>e?1:0)})};

LICENSE.txt

Copyright (c) 2011 Thomas Fuchs, http://mir.aculo.us
 
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.
 
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

package.json

{
  "name": "array_sort",
  "description": "Functional sorting of arrays",
  "keywords": [
    "array",
    "functional" 
  ]
}

AFAIK, the sort callback need not specifically return -1,0,1, but any Numeral. Therefore, you can shorten your function to

function(a,b,c){c=a.slice();return c.sort(function(d,e){d=b(d),e=b(e);return d-e})};

Btw, nice use of slice :-)

Regards, Alex

Variables c and rewrite of d and e are not needed:

function(a,b){return a.slice().sort(function(c,d){return b(c)-b(d)})}