输出函数名（最简方式）

 1 function getFnName(fn){
 2 return typeof fn !== ‘function‘?
 3        undefined:
 4        fn.name ||
 5       /function (.+)\(/.exec(fn + ‘‘)[1]
 6 }
 7
 8
 9 function Person(){}
10
11 var i = new Person();
12
13 var name = getFnName(i.constructor);
14
15 alert(name)