//*** This code is copyright 2004 by Gavin Kistner, !@phrogz.net
//*** It is covered under the license viewable at http://phrogz.net/JS/_ReuseLicense.txt
//*** Reuse or modification is free provided you abide by the terms of that license.
//*** (Including the first two lines above in your source code mostly satisfies the conditions.)


// Returns a function which can be used to sort an Array by multiple criteria.
// Can be called in one of three ways:
//   var sortFunc = SortBy( 'name' , 'age' , 'sex' );
//   var sortFunc = SortBy( ['name','age','sex'] );
//   var sortFunc = SortBy( { name:1, age:1, sex:1 } );
//
// The first two methods are equivalent, and sort in ascending order.
// The last method allows you to specify sort direction:
//   1 (or true)  specifies ascending sort order.
//   0 (or false) specifies descending sort order.
//
// The sort function is constructed using 'dot notation' for the properties;
// this means you can also specify a method to call on the object by putting
// parentheses at the end of the name.
// e.g. var stupidDateStringSort = SortBy('toDateString()','toTimeString()');

function SortBy(){
	var a=arguments, len=a.length, f='return ', p=1, i;
	if (len==1 && (a[0].constructor==Object || a[0].constructor==Array) && ((o=a=a[0]).constructor==Object)) p=0;
	if (p && (o={})) for (i=0,len=a.length;i<len;i++) o[a[i]]=1;
	for (k in o){
		var z=o[k]?['<','>']:['>','<'];
		f+='a.'+k+z[0]+'b.'+k+'?-1:a.'+k+z[1]+'b.'+k+'?1:';
	}
	return new Function('a','b',f+'0');
}


// Same as the function above, but uses .getAttribute() with the strings to find the value to sort by.
// (Needed when using custom attributes of XML objects for browsers other than IE.)
function SortByAttribute(){
	var a=arguments, len=a.length, f='return ', p=1, i;
	if (len==1 && (a[0].constructor==Object || a[0].constructor==Array) && ((o=a=a[0]).constructor==Object)) p=0;
	if (p && (o={})) for (i=0,len=a.length;i<len;i++) o[a[i]]=1;
	for (k in o){
		var z=o[k]?['<','>']:['>','<'];
		f+='a.getAttribute("'+k+'")'+z[0]+'b.getAttribute("'+k+'")?-1:a.getAttribute("'+k+'")'+z[1]+'b.getAttribute("'+k+'")?1:';
	}
	return new Function('a','b',f+'0');
}




/*********************************************************************************
*** EXAMPLES *********************************************************************

var people = [];
people.push( { name:'Bob' , age:15 , sex:'M' } );
people.push( { name:'Carol' , age:18 , sex:'F' } );
people.push( { name:'Sue' , age:33 , sex:'F' } );
people.push( { name:'Angie' , age:8 , sex:'F' } );
people.push( { name:'David' , age:12 , sex:'M' } );


var sortByName = SortBy('name');
people.sort( sortByName );

// people is now:
// [
//   {name:'Angie',age:8,sex:'F'},
//   {name:'Bob',age:15,sex:'M'},
//   {name:'Carol',age:18,sex:'F'},
//   {name:'David',age:12,sex:'M'},
//   {name:'Sue',age:33,sex:'F'}
// ]

var sortBySexThenAge = SortBy('sex','age');
people.sort( sortBySexThenAge );

// people is now:
// [
//   {name:'Angie',age:8,sex:'F'},
//   {name:'Carol',age:18,sex:'F'},
//   {name:'Sue',age:33,sex:'F'},
//   {name:'David',age:12,sex:'M'},
//   {name:'Bob',age:15,sex:'M'}
// ]


people.sort( SortBy({sex:0,name:0}) );

// people is now:
// [
//   {name:'David',age:12,sex:'M'},
//   {name:'Bob',age:15,sex:'M'},
//   {name:'Sue',age:33,sex:'F'},
//   {name:'Carol',age:18,sex:'F'},
//   {name:'Angie',age:8,sex:'F'}
// ]

people.sort( SortBy({name:0}) );

// people is now:
// [
//   {name:'Sue',age:33,sex:'F'},
//   {name:'David',age:12,sex:'M'},
//   {name:'Carol',age:18,sex:'F'},
//   {name:'Bob',age:15,sex:'M'},
//   {name:'Angie',age:8,sex:'F'}
// ]

*********************************************************************************/