1 原型鏈繼承

	//父類
	function Person(name,age){
		this.name = name || 'unknow'
		this.age = age || 0
	}

	//子類
	function Student(name){
		this.name = name
		this.score = 80
	}

	//繼承
	Student.prototype = new Person();
	Student.prototype.constructor = Student;
	

	var stu = new Student('lucy');
	console.log(stu.name);  //lucy  --子類覆蓋父類的屬性
	console.log(stu.age);   // 0    --父類的屬性
	console.log(stu.score);  // 80   --子類自己的屬性


*原型繼承共享引用型別(方法)*
共享方法可以,因為方法本身程式碼不變,就是被共享的. 但有些引用型別自身變化,如下
	//父類
	function Person(){
		this.hobbies = ['music','reading']
	}

	//子類
	function Student(){
	}

	//繼承
	Student.prototype = new Person();
	Student.prototype.constructor = Student;

	var stu1 = new Student();
	var stu2 = new Student();

	stu1.hobbies.push('basketball');

	console.log(stu1.hobbies);  // ["music", "reading", "basketball"]
	console.log(stu2.hobbies);  //  ["music", "reading", "basketball"]


 

2 建構函式繼承

*建構函式不共享引用型別和方法*
	
	//父類
	function Person(){
		this.hobbies = ['music','reading']
	}

	//子類
	function Student(){
		Person.call(this);
	}

	var stu1 = new Student();
	var stu2 = new Student();

	stu1.hobbies.push('basketball');

	console.log(stu1.hobbies);  // ["music", "reading", "basketball"]
	console.log(stu2.hobbies);  //  ["music", "reading"]

*建構函式可以給父類傳參*
	//父類
	function Person(name){
		this.name = name;
	}

	//子類
	function Student(name){
		Person.call(this,name);  //傳參Person(name)
	}

	var stu1 = new Student('lucy');
	var stu2 = new Student('lili');


	console.log(stu1.name);  //  lucy
	console.log(stu2.name);  //  lili

 

3 組合繼承
某些引用型別屬性使用建構函式繼承不共享，方法使用原型鏈繼承共享。
不論是建構函式還是原型鏈, 基本型別都是不共享的(基本型別與引用型別賦值的區別)

	//父類
	function Person(name){
		this.hobbies = ['music','reading'];
	}

	Person.prototype.say = function(){
		console.log('i am a person');
	}
	//子類
	function Student(name){
		Person.call(this);  //建構函式繼承（繼承屬性）本地hobbies
	}

	Student.prototype = new Person();  //原型繼承（繼承方法） 原型鏈hobbies和say
	Student.prototype.constructor = Student;

	//其實是本地hobbies比原型鏈的hobbies優先,實現組合繼承
	var stu1 = new Student('lucy');
	var stu2 = new Student('lili');

	stu1.hobbies.push('basketball');

	console.log(stu1.hobbies);  // ["music", "reading", "basketball"]
	console.log(stu2.hobbies);  // ["music", "reading"]

	console.log(stu1.say === stu2.say);  // true