javascript判断 对象 类型

/**
 * 返回一个对象的类型
 */
function getType(x) {
    //不能！x，因为"",0,false
    if (null == x)
        return "null";

    //注意：typeof对j引用类型对返回object
    var t = typeof x;
    if (t != "object")return t;

    //有的对象可能重写了toString方法，所以需要调用对象最原始的toString()
    var s = Object.prototype.toString.call(x),
            s = s.substring(8, s.length - 1);

    //注意：==“Object”的时候需要判断具体的类型。
    if (s != "Object")return s;

    var x_constructor = x.constructor;
    //x.constructor：即创建x对象的方法
    if (x_constructor == Object)return s;

    //一个对象的构造函数的原型对象中如定义有className属性（原本不存在的，这是用户您自己定义的属性），则返回这个属性的值
    //    function X(x,y,z){
    //        this.x=x;
    //    }
    //    X.prototype.className="X";
    //    var x=new X(1,2,3);
    //    alert(x.constructor.prototype== X.prototype)//return true.
    var x_cons_proto = x_constructor.prototype;
    if ("className" in x_cons_proto && typeof x_cons_proto.className == "string") {
        return x_cons_proto.className;
    }

    //返回构造函数的名称
    //但是只对于使用函数定义方式声明的函数有效,如：
    //function ClassA(){this.x="ss"}  var a=new ClassA(); alert(getType(a));
    if ("name" in x_constructor && "" != x_constructor.name)return x_constructor.name;

    /*下面都是闭包的情况*/
    //对与调用Function构造的方式创建的对象，则
    var c = x_constructor.toString(), c = c.substring(8, c.indexOf("(")).replace(/(^\s*)|(\s*$)/g, "");
    //对于new方法直接量方式创建的对象，则暂时无能为力
    if ("" == c) {
        return  "The object created by a anonymous function.";
    }

    return c;
}

/**
 * 测试
 */
var printFunc = function() {
    //--------------------------------------------------------------
    //--------------------------------------------------------------
    var k;                     //<br>
    document.writeln(getType(k));
    k = "";
    document.writeln(getType(k));
    k = 23;
    document.writeln(getType(k));
    k = true;
    document.writeln(getType(k));
    k = new Date();
    document.writeln(getType(k));
    k = /\s/;
    document.writeln(getType(k));
    document.writeln("<br>");
    document.writeln("<br>");
    document.writeln("<br>");

    //--------------------------------------------------------------
    //--------------------------------------------------------------
    function Outer(x) {
        var x = x;
        //... ...
        return function() {
            return x;
        }
    }

    document.writeln(getType(Outer));
    var o = Outer(98);
    document.writeln(getType(o));
    var o = new Outer;
    document.writeln(getType(o));
    var o = new Outer(33);
    document.writeln(getType(o));
    document.writeln("<br>");
    document.writeln("<br>");
    document.writeln("<br>");

    //--------------------------------------------------------------
    //--------------------------------------------------------------
    function Outer2(x) {
        this.x = x;
        //... ...
        this.getX = function() {
            return x;
        }
    }

    document.writeln(getType(new Outer2(99)));
    document.writeln("<br>");
    document.writeln("<br>");
    document.writeln("<br>");

    //--------------------------------------------------------------
    //--------------------------------------------------------------
    function Outer3(x) {
        this.x = x;
        //... ...
        this.getX = function() {
            return x;
        }
        return x;
    }

    document.writeln(getType(new Outer3(92)));
    document.writeln("<br>");
    document.writeln("<br>");
    document.writeln("<br>");

    //--------------------------------------------------------------
    //--------------------------------------------------------------
    function MyClass(x, y) {
        this.x = x;
        this.y = y;
    }

    //MyClass.prototype.className = "MyClass"; //自定义一个属性，表示类型，则会提高执行效率
    //MyClass.prototype.constructor = MyClass;
    MyClass.prototype.getSum = function() {
        return this.x + this.y;
    };
    var mc = new MyClass(2, 5);

    document.writeln(mc.getSum());
    document.writeln(getType(mc));
    document.writeln("<br>");
    document.writeln("<br>");
    document.writeln("<br>");

    //--------------------------------------------------------------
    //--------------------------------------------------------------
    var MyClass3 = function(x, y) {
        this.x = x;
        this.y = y;
    }
    //MyClass.prototype.className = "MyClass";
    //MyClass.prototype.constructor = MyClass;
    MyClass3.prototype.getSum = function() {
        return this.x + this.y;
    };
    mc = new MyClass3(1, 5);

    document.writeln(mc.getSum());
    document.writeln(getType(mc));
    document.writeln("<br>");
    document.writeln("<br>");
    document.writeln("<br>");
    //--------------------------------------------------------------

    //--------------------------------------------------------------
    var MyClass2 = Function("x", "y", "this.x = x;this.y = y;");
    MyClass2.prototype.getSum = function() {
        return this.x + this.y;
    };
    mc = new MyClass2(3, 5);
    document.writeln(mc.getSum());
    document.writeln(getType(mc));
}


printFunc();

//document.writeln("<br>");
//document.writeln(printFunc);