# 构造器模式

> Constructor Pattern

## 知识点一：有四种方法可以把键值对赋值给一个对象

```javascript
//ECMAScript 3 
//1. 点语法
// Set properties
newObject.someKey = "Hello World";

// Get properties
var value = newObject.someKey;

// 2. 中括号访问

// Set properties
newObject["someKey"] = "Hello World";

// Get properties
var value = newObject["someKey"];

//ECMAScript 5

// 3. Object.defineProperty
// Set properties
Object.defineProperty( newObject, "someKey", {
    value: "for more control of the property's behavior",
    writable: true,
    enumerable: true,
    configurable: true
});

// 4. Object.defineProperties
// Set properties
Object.defineProperties( newObject, {

  "someKey": {
    value: "Hello World",
    writable: true
  },

  "anotherKey": {
    value: "Foo bar",
    writable: false
  }

});
```

## 知识点二：简单的构建模式

```javascript
function Car( model, year, miles ) {

  this.model = model;
  this.year = year;
  this.miles = miles;

  this.toString = function () {
    return this.model + " has done " + this.miles + " miles";
  };
}

// Usage:

// We can create new instances of the car
var civic = new Car( "Honda Civic", 2009, 20000 );
var mondeo = new Car( "Ford Mondeo", 2010, 5000 );

// and then open our browser console to view the
// output of the toString() method being called on
// these objects
console.log( civic.toString() );
console.log( mondeo.toString() );
```

## 知识点三：带原型的构建模式

```javascript
function Car( model, year, miles ) {

  this.model = model;
  this.year = year;
  this.miles = miles;

}


// Note here that we are using Object.prototype.newMethod rather than
// Object.prototype so as to avoid redefining the prototype object
Car.prototype.toString = function () {
  return this.model + " has done " + this.miles + " miles";
};

// Usage:

var civic = new Car( "Honda Civic", 2009, 20000 );
var mondeo = new Car( "Ford Mondeo", 2010, 5000 );

console.log( civic.toString() );
console.log( mondeo.toString() );
```


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