var emptyObject1 = {}; //创建空对象
var emptyObject2 = new Object(); //创建空对象
var person = {"name":"sdcyst",
"age":18,
"sex":"male"}; //创建一个包含初始值的对象person
alert(person.name); //sdcyst
alert(person["age"]); //18
var person = {};
person.name = "sdcyst";
person["age"] = 18;
alert(person.name + "__" + person.age); //sdcyst__18
var _person = {name:"balala","age":23}; //在构建一个对象时,属性的名字可以不用引号来标注(name),
//但是仍旧是一个字符串类型.在访问的时候[]内仍旧需要引号
alert(_person["name"] + "__" + person.age); //balala__23
alert(_person[name]); //undefinied
var name = {"name1":"NAME1","name2":"NAME2","name3":"NAME3","name4":"NAME4"};
var namestring = "";
for(var props in name) { //循环name对象中的属性名字
namestring += name[props];
}
alert(namestring); //NAME1NAME2NAME3NAME4
namestring = "";
for(var i=0; i<4; i++) {
namestring += name["name"+(i+1)];
}
alert(namestring); //NAME1NAME2NAME3NAME4
var name = {"name1":"NAME1","name2":"NAME2","name3":"NAME3","name4":"NAME4"};
var namestring = "";
for(var props in name) { //循环name对象中的属性名字
namestring += name[props];
}
alert(namestring); //NAME1NAME2NAME3NAME4
delete name.name1; //删除name1属性
delete name["name3"]; //删除name3属性
namestring = "";
for(var props in name) { //循环name对象中的属性名字
namestring += name[props];
}
alert(namestring); //NAME2NAME4
alert("name1" in name); //false
alert("name4" in name); //true
var date = new Date();
alert(date.constructor); //Date
alert(date.constructor == "Date"); //false
alert(date.constructor == Date); //true
var array1 = []; //创建空数组
var array2 = new Array(); //创建空数组
array1 = [1,"s",[3,4],{"name1":"NAME1"}]; //
alert(array1[2][1]); //4 访问数组中的数组元素
alert(array1[3].name1); //NAME1 访问数组中的对象
alert(array1[8]); //undefined
array2 = [,,]; //没有数值填入只有逗号,则对应索引处的元素为undefined
alert(array2.length); //3
alert(array2[1]); //undefined
var array = new Array(10);
alert(array.length); //10
alert(array[4]); //undefined
array[100] = "100th"; //这个操作会改变数组的长度,同时将10-99索引对应的值设为undefined
alert(array.length); //101
alert(array[87]); //undefined
var array = new Array("n1","n2","n3","n4","n5"); //五个元素的数组
var astring = "";
for(var i=0; i<array.length; i++) { //循环数组元素
astring += array[i];
}
alert(astring); //n1n2n3n4n5
delete array[3]; //删除数组元素的值
alert(array.length + "_" + array[3]) //5_undefined
array.length = 3; //缩减数组的长度
alert(array[3]); //undefined
array.length = 8; //扩充数组的长度
alert(array[4]); //undefined
var array = new Array("no1","no2");
array["po"] = "props1";
alert(array.length); //2
//对于数组来说,array[0]同array["0"]效果是一样的(?不确定,测试时如此)
alert(array[0] + "_" + array["1"] + "_" + array.po);//no1_no2_props1
function myprint(s1,s2,s3) {
alert(s1+"_"+s2+"_"+s3);
}
myprint(); //undefined_undefined_undefined
myprint("string1","string2"); //string1_string2_undefined
myprint("string1","string2","string3","string4"); //string1_string2_string3
function myprint(s1,person) {
var defaultperson = { //默认person对象
"name":"name1",
"age":18,
"sex":"female"
};
if(!s1) { //s1不允许为空
alert("s1 must be input!");
return false;
}
person = person || defaultperson; //接受person对象参数
alert(s1+"_"+person.name+":"+person.age+":"+person.sex);
};
myprint(); //s1 must be input!
myprint("s1"); //s1_name1:18:female
myprint("s1",{"name":"sdcyst","age":23,"sex":"male"}); //s1_sdcyst:23:male
function myargs() {
alert(arguments.length);
alert(arguments[0]);
}
myargs(); //0 --- undefined
myargs("1",[1,2]); //2 --- 1
function(x) {
if (x <= 1) return 1;
return x * arguments.callee(x-1);
} (section8.2)
var obj = {f0:function(){alert("f0");}}; //对象包含一个方法
function f1() {alert("f1");}
obj.f1 = f1; //为对象添加方法
obj.f0(); //f0 f0是obj的方法
obj.f1(); //f1 f1是obj的方法
f1(); //f1 f1同时又是一个函数,可以直接调用
f0(); //f0仅仅是obj的方法,只能通过对象来调用
var obj = {"name":"NAME","sex":"female"};
obj.print = function() { //为对象添加方法
alert(this.name + "_" + this["sex"]);
};
obj.print(); //NAME_female
obj.sex = "male";
obj.print(); //NAME_male
var person = {name:"defaultname",
setName:function(s){
this.name = s;
},
"printName":function(){
alert(this.name);
}}
person.printName(); //defaultname
person.setName("newName");
person.printName(); //newName
function Person(name,sex) {
this.name = name;
this.sex = sex;
}
var per = new Person("sdcyst","male");
alert("name:"+per.name+"_sex:"+per.sex); //name:sdcyst_sex:male
function Person(name,sex) { //构造函数
this.name = name;
this.sex = sex;
}
Person.prototype.age = 12; //为prototype属性对应的prototype对象的属性赋值
Person.prototype.print = function() { //添加方法
alert(this.name+"_"+this.sex+"_"+this.age);
};
var p1 = new Person("name1","male");
var p2 = new Person("name2","male");
p1.print(); //name1_male_12
p2.print(); //name2_male_12
Person.prototype.age = 18; //改变prototype对象的属性值,注意是操作构造函数的prototype属性
p1.print(); //name1_male_18
p2.print(); //name2_male_18
function Person(name,sex) { //Person类的构造函数
this.name = name;
this.sex = sex;
}
Person.prototype.age = 12; //为Person类的prototype属性对应的prototype对象的属性赋值,
//相当于为Person类的父类添加属性
Person.prototype.print = function() { //为Person类的父类添加方法
alert(this.name+"_"+this.sex+"_"+this.age);
};
var p1 = new Person("name1","male"); //p1的age属性继承子Person类的父类(即prototype对象)
var p2 = new Person("name2","male");
p1.print(); //name1_male_12
p2.print(); //name2_male_12
p1.age = 34; //改变p1实例的age属性
p1.print(); //name1_male_34
p2.print(); //name2_male_12
Person.prototype.age = 22; //改变Person类的超类的age属性
p1.print(); //name1_male_34(p1的age属性并没有随着prototype属性的改变而改变)
p2.print(); //name2_male_22(p2的age属性发生了改变)
p1.print = function() { //改变p1对象的print方法
alert("i am p1");
}
p1.print(); //i am p1(p1的方法发生了改变)
p2.print(); //name2_male_22(p2的方法并没有改变)
Person.prototype.print = function() { //改变Person超类的print方法
alert("new print method!");
}
p1.print(); //i am p1(p1的print方法仍旧是自己的方法)
p2.print(); //new print method!(p2的print方法随着超类方法的改变而改变)
function Person(name,age) { //定义方法
this.name = name;
this.age = age;
}
var o = new Object(); //空对象
alert(o.name + "_" + o.age); //undefined_undefined
Person.call(o,"sdcyst",18); //相当于调用:o.Person("sdcyst",18)
alert(o.name + "_" + o.age); //sdcyst_18
Person.apply(o,["name",89]);//apply方法作用同call,不同之处在于传递参数的形式是用数组来传递
alert(o.name + "_" + o.age); //name_89
Person.counter = 0; //定义类变量,创建的Person实例的个数
function Person(name,age) {
this.name = name;
this.age = age;
Person.counter++; //没创建一个实例,类变量counter加1
};
Person.whoIsOlder = function(p1,p2) { //类方法,判断谁的年龄较大
if(p1.age > p2.age) {
return p1;
} else {
return p2;
}
}
var p1 = new Person("p1",18);
var p2 = new Person("p2",22);
alert("现在有 " + Person.counter + "个人"); //现在有2个人
var p = Person.whoIsOlder(p1,p2);
alert(p.name + "的年龄较大"); //p2的年龄较大
function Circle(radius) {
this.radius = radius;
this.area = function() {
return 3.14 * this.radius * this.radius;
}
}
var c = new Circle(1);
alert(c.area()); //3.14
function Circle(radius) {
this.radius = radius;
}
Circle.prototype.area = function() {
return 3.14 * this.radius * this.radius;
}
var c = new Circle(1);
alert(c.area()); //3.14
function Circle(radius) { //定义父类Circle
this.radius = radius;
}
Circle.prototype.area = function() { //定义父类的方法area计算面积
return this.radius * this.radius * 3.14;
}
function PositionCircle(x,y,radius) { //定义类PositionCircle
this.x = x; //属性横坐标
this.y = y; //属性纵坐标
Circle.call(this,radius); //调用父类的方法,相当于调用this.Circle(radius),设置PositionCircle类的
//radius属性
}
PositionCircle.prototype = new Circle(); //设置PositionCircle的父类为Circle类
var pc = new PositionCircle(1,2,1);
alert(pc.area()); //3.14
//PositionCircle类的area方法继承自Circle类,而Circle类的
//area方法又继承自它的prototype属性对应的prototype对象
alert(pc.radius); //1 PositionCircle类的radius属性继承自Circle类
/*
注意:在前面我们设置PositionCircle类的prototype属性指向了一个Circle对象,
因此pc的prototype属性继承了Circle对象的prototype属性,而Circle对象的constructor属
性(即Circle对象对应的prototype对象的constructor属性)是指向Circle的,所以此处弹出
的是Circ.
*/
alert(pc.constructor); //Circle
/*为此,我们在设计好了类的继承关系后,还要设置子类的constructor属性,否则它会指向父类
的constructor属性
*/
PositionCircle.prototype.constructor = PositionCircle
alert(pc.constructor); //PositionCircle
var sco = "global"; //全局变量
function t() {
var sco = "local"; //函数内部的局部变量
alert(sco); //local 优先调用局部变量
}
t(); //local
alert(sco); //global 不能使用函数内的局部变量
function f(props) {
for(var i=0; i<10; i++) {}
alert(i); //10 虽然i定义在for循环的控制语句中,但在函数
//的其他位置仍旧可以访问该变量.
if(props == "local") {
var sco = "local";
alert(sco);
}
alert(sco); //同样,函数仍可引用if语句内定义的变量
}
f("local"); //10 local local
var sco = "global";
function print1() {
alert(sco); //global
}
function print2() {
var sco = "local";
alert(sco); //local
}
function print3() {
alert(sco); //undefined
var sco = "local";
alert(sco); local
}
print1(); //global
print2(); //local
print3(); //undefined local
function print3() {
var sco;
alert(sco);
sco = "local";
alert(sco);
}
var scope = "global" //定义全局变量
function print() {
alert(scope);
}
function change() {
var scope = "local"; //定义局部变量
print(); //虽然是在change函数的作用域内调用print函数，
//但是print函数执行时仍旧按照它定义时的作用域起作用
}
change(); //golbal
var i = 0;
function getNext() {
i++;
return i;
}
alert(getNext()); //1
alert(getNext()); //2
alert(getNext()); //3
function temp() {
var i = 0;
function b() {
return ++i;
}
return b;
}
var getNext = temp();
alert(getNext()); //1
alert(getNext()); //2
alert(getNext()); //3
alert(getNext()); //4
function Person(name, age) {
this.getName = function() { return name; };
this.setName = function(newName) { name = newName; };
this.getAge = function() { return age; };
this.setAge = function(newAge) { age = newAge; };
}
var p1 = new Person("sdcyst",3);
alert(p1.getName()); //sdcyst
alert(p1.name); //undefined 因为Person('类')没有name属性
p1.name = "mypara" //显示的给p1添加name属性
alert(p1.getName()); //sdcyst 但是并不会改变getName方法的返回值
alert(p1.name); //mypara 显示出p1对象的name属性
p1.setName("sss"); //改变私有的"name"属性
alert(p1.getName()); //sss
alert(p1.name); //仍旧为mypara
Ref:Javascript研究小组知识库
