function factorial(n){if(n<=1){return 1;}else{return n*arguments.callee(n-1);}} 

  function factorial(n){if(n<=1){return 1;}else{return n*factorial(n-1);}}alert(factorial(3));//求3的阶乘

 var f=factorial;factorial=null;alert(f(3));

var factorial=(function f(n){if(n<=1){return 1;}else{return n*f(n-1);}}); var anotherF=factorial;factorial=null;alert(anotherF(2));