• Undefined   未被定义类型
• Boolean      布尔类型
• String         字符串类型
• Number      数字类型
• Object        引用类型
• Function     方法类型

• 当text=0时，打印出Number；当为空字符串时打印出string,为null打印出object

var text = 0;alert(typeof text)

• 如果不赋值或赋值null或赋值undefined，则都是打印出的true,

var u
        alert(u == undefined);

var s = "hello";var b = Boolean(s);alert(b);

var b = null;alert(Number(b));

 var s = "123.567";alert(parseFloat(s));

      var name = 'Join';var num = 123;alert( typeof  (name+num));

var b = true;alert(b.toString());alert(name.toLocaleString());

 function SayHi(name, message){alert("Hello"+name+"mesg:"+message);}SayHi("Rocky", "123");

function howManyArgs(){alert(arguments[0]+arguments[1]+arguments[2]);}howManyArgs(1,2,3);

for (var i = 0; i < 10; i++){}alert(i);

  var colors = new Array(3);//设置数组的长度。colors[0] = "red";colors[1] = "blue";colors[2] = "yellow";for (var i = 0; i <colors. length; i++)//遍历出来
        {alert(colors[i]);}

var colors1 = new Array("red", "blue", "yellow");for (var i = 0; i < colors1.length; i++){alert(colors[i]);}

        var colo = ["red", "blue", "yellow"];colo.push("张三", "李四");        colo.pop();                      alert(colo.shift());            alert(colo);

var str = "Woshiunib";alert(str.substring(1, 3));alert(str.substr(1, 3)); 

var values = [1, 3, 2, -9, 5, 11];function compare(v1, v2) {if (v1 < v2) {return -1;}else if (v1 > v2) {return 1;}else {return 0;}}values.sort(compare);     alert(values);

var values = [1, 3, 2, -9, 5, 11];function compare(v1, v2) {if (v1 < v2) {return 1;}else if (v1 > v2) {return -1;}else {return 0;}}values.sort(compare);     alert(values);

var values = [1, 3, 2, -9, 5, 11];function compare(v1, v2) {if (v1 < v2) {return 1;}else if (v1 > v2) {return -1;}else {return 0;}}  values.reverse(values);alert(values);

var num1 = "Hello";alert(isNaN(num1));