JavaScript 設(shè)計(jì)模式之構(gòu)造函數(shù)模式

function Car(model, year, miles) {
    this.model = model;
    this.year = year;
    this.miles = miles;
    this.output= function () {
        return this.model + "走了" + this.miles + "公里";
    };
}

var tom= new Car("大叔", 2009, 20000);
var dudu= new Car("Dudu", 2010, 5000);

console.log(tom.output());
console.log(dudu.output());

function Car(model, year, miles) {
    this.model = model;
    this.year = year;
    this.miles = miles;
    this.output= formatCar;
}

function formatCar() {
    return this.model + "走了" + this.miles + "公里";
}

function Car(model, year, miles) {
    this.model = model;
    this.year = year;
    this.miles = miles;
}

/
注意：這里我們使用了Object.prototype.方法名，而不是Object.prototype
主要是用來(lái)避免重寫定義原型prototype對(duì)象
/
Car.prototype.output= function () {
    return this.model + "走了" + this.miles + "公里";
};

var tom = new Car("大叔", 2009, 20000);
var dudu = new Car("Dudu", 2010, 5000);

console.log(tom.output());
console.log(dudu.output());

function Car(model, year, miles) {
    this.model = model;
    this.year = year;
    this.miles = miles;
    // 自定義一個(gè)output輸出內(nèi)容
    this.output = function () {
        return this.model + "走了" + this.miles + "公里";
    }
}

//方法1：作為函數(shù)調(diào)用
Car("大叔", 2009, 20000);  //添加到window對(duì)象上
console.log(window.output());

//方法2：在另外一個(gè)對(duì)象的作用域內(nèi)調(diào)用
var o = new Object();
Car.call(o, "Dudu", 2010, 5000);
console.log(o.output()); 

//作為函數(shù)調(diào)用
var tom = Car("大叔", 2009, 20000);
console.log(typeof tom); // "undefined"
console.log(window.output()); // "大叔走了20000公里"

//使用new 關(guān)鍵字
var tom = new Car("大叔", 2009, 20000);
console.log(typeof tom); // "object"
console.log(tom.output()); // "大叔走了20000公里"

function Car(model, year, miles) {
    if (!(this instanceof Car)) {
        return new Car(model, year, miles);
    }
    this.model = model;
    this.year = year;
    this.miles = miles;
    this.output = function () {
        return this.model + "走了" + this.miles + "公里";
    }
}

var tom = new Car("大叔", 2009, 20000);
var dudu = Car("Dudu", 2010, 5000);

console.log(typeof tom); // "object"
console.log(tom.output()); // "大叔走了20000公里"
console.log(typeof dudu); // "object"
console.log(dudu.output()); // "Dudu走了5000公里"

// 使用原始包裝函數(shù)
var s = new String("my string");
var n = new Number(101);
var b = new Boolean(true);

// 推薦這種
var s = "my string";
var n = 101;
var b = true;

// 原始string
var greet = "Hello there";
// 使用split()方法分割
greet.split(' ')[0]; // "Hello"
// 給原始類型添加新屬性不會(huì)報(bào)錯(cuò)
greet.smile = true;
// 單沒(méi)法獲取這個(gè)值（18章ECMAScript實(shí)現(xiàn)里我們講了為什么）
console.log(typeof greet.smile); // "undefined"

// 原始string
var greet = new String("Hello there");
// 使用split()方法分割
greet.split(' ')[0]; // "Hello"
// 給包裝函數(shù)類型添加新屬性不會(huì)報(bào)錯(cuò)
greet.smile = true;
// 可以正常訪問(wèn)新屬性
console.log(typeof greet.smile); // "boolean"