JavaScript currying function

jscurry.js

function curry(fn, args, len) {  
  var fnStr = fn.toString(), 
      argStart = fnStr.indexOf('(') + 1;    argnames = fnStr.substr(argStart,  fnStr.indexOf(')') - argStart).split(/[ ,]+/); 
  len = len?len:argnames.length

  return function() {
    var a = [], i = 0;
    for (var k = 0; k < len; ++k) 
      if (args.hasOwnProperty(k))
        a.push(args[k])
      else if (args.hasOwnProperty(argnames[k]))
        a.push(args[argnames[k]])
      else a.push(arguments[i++])           
    return fn.apply(this, a);    
  }
}