function argumentNames(fn){
       //查找参数列表
       var found = /^[\s\(]*function[^(]*\(\s*([^)]*?)\s*\)/.exec(fn.toString());
       //分隔参数列表
       return found && found[1] ? found[1].split(/,\s*/) : [];
};

alert(argumentNames(function(){}).length === 0);
alert(argumentNames(function(x){})[0] === ‘x‘);

var results = argumentNames(function(a,b,c,d,e){});
alert(results[0] == ‘a‘ &&
       results[1] == ‘b‘ &&
       results[2] == ‘c‘ &&
       results[3] == ‘d‘ &&
       results[4] == ‘e‘);