//*** This code is copyright 2003 by Gavin Kistner, gavin@refinery.com
//*** 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 satisfies the conditions.)

// Sort an array of objects by multiple criteria
// Pass in a single array of parameters, or multiple individual parameters
// Each parameter may be a string name for the property, or a custom object with a single property;
//     the property value is 0 to sort descending, 1 to sort ascending
// (See examples below.)
// Returns a function pointer suitable for passing to Array.sort(...);


// Note that this function calls  new Function(...)  which is akin to eval() and
// hence horrid, gross, terrible, shitty, slutty, and uneducative. But it does.


function SortBy(){
	var args = (arguments.length==1 && arguments[0].constructor==Array)?arguments[0]:arguments;
	var body = "return ";
	for (var i=0,len=args.length;i<len;i++){
		var param = args[i];
		if (typeof(param)=='string'){
			var colName=param;
			var sortAsc=1;
		} else for (var colName in param) sortAsc = param[colName];
		body+='a.'+colName+(sortAsc?'<':'>')+"b."+colName+"?-1:a."+colName+(sortAsc?'>':'<')+"b."+colName+"?1:";
	}
	return new Function('a','b',body+0);
}


/* EXAMPLES ********************************************************
var people = [
	{ name:'Bob',   age:12, weight:1   },
	{ name:'Gavin', age:30, weight:170 },
	{ name:'Susan', age:19, weight:120 },
	{ name:'Lisa',  age:29, weight:135 },
	{ name:'Lisa',  age:45, weight:150 },
	{ name:'Dave',  age:12, weight:170 },
];

people.sort(  SortBy('name','age') );
// Same as: people.sort( SortBy( ['name','age'] ) );
//	{name:'Bob',age:12,weight:1},
//	{name:'Dave',age:12,weight:170},
//	{name:'Gavin',age:30,weight:170},
//	{name:'Lisa',age:29,weight:135},
//	{name:'Lisa',age:45,weight:150},
//	{name:'Susan',age:19,weight:120}

people.sort(  SortBy( {age:0}, {weight:1} )  );
//	{name:'Lisa',age:45,weight:150},
//	{name:'Gavin',age:30,weight:170},
//	{name:'Lisa',age:29,weight:135},
//	{name:'Susan',age:19,weight:120},
//	{name:'Bob',age:12,weight:1},
//	{name:'Dave',age:12,weight:170}

// You can even mix strings with object/sort direction pairs
people.sort( SortBy( 'age' , {name:0} ) );
people.sort( SortBy( ['age',{name:0}] ) );
******************************************************************/