Javascript 有用参考函数

 /*
        Append the names of the enumerable properties of object o to the array a, and return a.
        If a is omitted or null, create and return a new array
        */
        function copyPropertyNamesToArray(o, /*optional*/a) {
            if (!a) a = [];  ///If undefined or null , use a blank array
            for (var perperty in o) a.push(perperty)
            return;
        }

        /*
        arguments 类似 Math.max()
        */
        function max(/*.....*/) {
            var m = Number.NEGATIVE_INFINITY;
            ////Loop through all the arguments , looking for, and 
            //// remembering, the biggest
            for (var i = 0; i < arguments.length; i++)
                if (arguments[i] > m) m = arguments[i];
            return m;
        }


        /*
        判断传递给函数的参数个数是否符合要求
        */
        function check(args) {
            var actual = args.length;
            var expected = args.callee.length;
            if (actual != expected) {
                throw new Error("Wrong number of arguments: expected: " + expected + "; actually passed " + actual);
            }
        }

        function f(x, y, z) {
            check(arguments);
            return x + y + z;
        }

        /*
        程序员偶尔会想要编写一个通过调用来记住一个值的函数。这个值不能存储在一个局部变量中，因为调用对象不能通过调用来维持。尽量不用全局变量
        */
        uniqueId = function () {
            if (!arguments.callee.id) arguments.callee.id = 0;
            return arguments.callee.id++;
        }

        CuniqueId = (function () { //The call object of this function holds our value
            var id = 0;            //this is the private persistent value
            // The outer function returns a nested function that has access
            // to the persistent value. It is the nested function we're storing
            // in the variable uniqueId above
            return function () { return id++ }; //Return and increment
        })();   //Invoke the outer function after defining it.