今天R神打电话跟我说 Js面向对象。下午又不想研究对讲的程序。学一下吧
Js 创建对象的几种方法。
1. 这里先定义o为一个空的对象,然后为o设置了一堆属性。
function createPerson(name,age,job){
var o = {};
o.name = name;
o.age = age;
o.job = job;
o.sayName = function(){
alert(this.name);
};
return o;
}
var tanya = createPerson("tanya","30","female");
var ansel = createPerson("ansel","30","male");
tanya.sayName();
ansel.sayName();
2.其实也可以直接给o属性的嘛,所以如果这样写也是ok的。
function createPerson(name,age,job){
var o = {
name : name,
age : age,
job : job,
sayName : function(){
alert(this.name);
}
};
return o;
}
var tanya = createPerson("tanya","30","female");
var ansel = createPerson("ansel","30","male");
tanya.sayName();
ansel.sayName();
3.还有一种办法是利用无敌的this,因为this就表示当前运行时的对象,将构造函数this的作用域指向新对象,将当前运行对象的属性和方法都赋给新对象,这样对象模式称为构造函数模式
function Person(name,age,job){
this.name = name;
this.age = age;
this.job = job;
this.sayName = function(){
alert(this.name);
};
}
var tanya = new Person("tanya","30","female");
var ansel = new Person("ansel","30","male");
tanya.sayName();
ansel.sayName();
4. 考虑下下面的情况
function Person(name,age,job){
this.name = name;
this.age = age;
this.job = job;
this.sayName = function(){
alert(this.name);
};
}
Person("tanya","30","female");
Person("ansel","30","male");
window.sayName();
window.sayName();
发现两次弹出的都是ansel,这是因为不用new的话,就不是一个person的实例,而仅仅在执行函数。而在全局作用域调用一个函数时this总是指向Global对象。而Global对象在浏览器中就是window对象。
我们还可以用构造模式在另外一个对象中调用sayName方法,还记得Apply和call么,来吧再考虑另外一种情况,
5.
function Person(name,age,job){
this.name = name;
this.age = age;
this.job = job;
this.sayName = function(){
alert(this.name);
};
}
var olivia = {};
Person.call(olivia,"tanya","30","female");
olivia.sayName();
var philip = {}
Person.apply(philip,["ansel","30","male"]);
philip.sayName();
6.原型模式就要考虑原型链了,分析一下,sayName方法在实例中被重复定义了两次,但其实没有必要创造两个一样的副本。使用原型方法,可以使是tanya和ansel的共享一个sayName方法。
于是原型模式的写法如下:
function Person(name,age,job){
this.name = name;
this.age = age;
this.job = job;
}
Person.prototype.sayName= function(){
alert(this.name);
};
var tanya = new Person("tanya","30","female");
var ansel = new Person("ansel","30","male");
tanya.sayName();
ansel.sayName();
7. 应该还可以这么写。
function Person(name, age, job) {
this.name = name;
this.age = age;
this.job = job;
if (typeof sayName != "function") {
this.sayName = function () {
alert(this.name);
}
}
}
var tanya = new Person("tanya", "30", "female");
var ansel = new Person("ansel", "30", "male");
tanya.sayName = function () {
alert("Hello");
};
tanya.sayName();
ansel.sayName();
小结:函数的call,apply 方法。