/* 函数的定义 */ function a() { return 1; } var b = function () { return 1; }; var c = function d() { return 1; }; // d === undefined var e = new Function("return 1;"); alert(typeof a); //function alert(typeof b); //function alert(typeof c); //function alert(typeof d); //undefined alert(typeof e); //function alert(a() + b() + c() + e()); //4 /* 函数自执行 */ (function (a, b) { alert(a + b); }) (1, 2); //3 (function (a, b) { alert(a + b); } (1, 2)); //3 var f = function (a, b) { alert(a + b); } (1, 2); //3; f === undefined