js創建對象的方法:
1.工廠模式;
function createPerson(name, age, job) {
var o = new Object();
o.name = name;
o.age = age;
o.job = job;
o.sayName = function() {
alert(this.name);
}
return o;
}
var person1 = createPerson("lily", 29, "Engineer");
var person2 = createPerson("lucy", 20, "Student");
person1.sayName();
person2.sayName();
缺點:不知道對象類型
2.構造函數模式;
function Person(name, age, job) {
this.name = name;
this.age = age;
this.job = job;
this.sayName = function() {
alert(this.name);
}
}
var person1 = new Person(("lily", 29, "Engineer");
var person2 = new Person("lucy", 20, "Student");
缺點:每個方法都要在每個實例上重新創建一遍,造成了內存上的浪費。(這兩個方法是不同的作用域鏈)
3.原型模式;
function Person() {
}
Person.prototype.name = "hehe";
Person.prototype.age = 29;
Person.prototype.job = "Engineer";
Person.prototype.sayName = function() {
alert(this.name);
}
var person1 = new Person();
person1.name = "lily";
person1.sayName();
var person2 = new Person();
person2.sayName();
上面每添加一個屬性和方法都需要.prototype.,封裝性不好,故做如下改進(重寫構造函數,此時,):
function Person() {
}
Person.prototype = {
constructor: Person, // 會導致[[Enumerable]]屬性被設置爲true
name: "hehe",
age: 29,
friends: ["HanMeimei", "LiLei"],
sayName: function() {
alert(this.name);
}
}
Person.prototype.age = 29;
Person.prototype.job = "Engineer";
Person.prototype.sayName = function() {
alert(this.name);
}
var person1 = new Person();
person1.friends.push("Susan");
var person2 = new Person();
console.log("person2.friends:",person2.friends);
缺點:由於原型模式就是多個實例共享屬性和方法的,那麼針對引用類型的屬性而言,多個實例的引用類型是會相互影響的
4.組合使用構造函數模式和原型模式:這是一般常用的方式,用構造函數定義實例屬性,用原型創建公共屬性和方法:
function Person(name, age, job) {
this.name = name;
this.age = age;
this.job = job;
this.friends = ["HanMeimei", "LiLei"];
}
Person.prototype = {
constructor: Person,
sayName: function() {
alert(this.name);
}
}
var person1 = new Person();
person1.friends.push("Susan");
var person2 = new Person();
console.log("person2.friends:",person2.friends);
這樣引用類型的屬性便不會有問題了。
缺點:上述沒有面向對象,構造函數和原型是分開的,沒有將其封裝。而動態原型模式就可以解決此問題。
5.動態原型模式;此方式就是完美的,也常用
function Person(name, age, job) {
this.name = name;
this.age = age;
this.job = job;
this.friends = ["HanMeimei", "LiLei"];
if (typeof this.sayName !== "function") { // 確保在多個實例初始化時只創建一次
Person.prototype.sayName = function() { // 此處不能重寫原型,會切換了實例與原型之間的聯繫
alert(this.name);
};
Person.prototype.sayAge = function() {
alert(this.name);
};
}
}
var person1 = new Person();
person1.friends.push("Susan");
var person2 = new Person();
console.log("person2.friends:",person2.friends);
6.寄生構造函數模式;
與工廠模式比較類似,當其他模式都不能用的時候,再採用寄生構造函數模式,可以用其爲對象創建構造函數
function Person(name, age, job) { //與工廠模式的區別 此處是構造函數,然後new 出來的
var o = new Object();
o.name = name;
o.age = age;
o.job = job;
o.sayName = function() {
alert(this.name);
}
return o;
}
var person1 = new Person("HanMeimei", 29, "Engineer");
person1.sayName();
e.g.爲對象創建構造函數
function SpecialArray() {
var arr = new Array();
arr.push.apply(arr, arguments);
arr.toPipedString = function() {
return this.join("|");
}
return arr;
}
var colors = new SpecialArray("red", "yellow");
console.log("colors:",colors.toPipedString());
7.穩妥構造函數模式:就是沒有this的概念,屬性只能從方法中獲取,這適合在安全執行環境中使用.
function Person(name, age, job) {
var o = new Object();
o.sayName = function() {
alert(name)
}
return o;
}
var person1 = Person("hehe");
person1.sayName();
工廠模式、寄生構造函數模式與穩妥構造函數模式很類似