js原型继承仅可继承实例而非构造器

js原型继承继承构造器带来的缺点

• 修改Person构造器会影响到继承他的子类

function Person(){this.sex = 'man'};
function Man(){};
Man.prototype = Person;

var m1 = new Man();
m1.sex;//'man'

// 修改Person构造器会影响到继承他的子类
delete Person.sex;
m1.sex;//undefined

js原型继承继承构造器实例避免缺点

function Person(){this.sex = 'man'};
function Man(){};
Man.prototype = new Person();
Man.prototype.construct = Man;

var m1 = new Man();
m1.sex;//'man'

// 修改Person构造器不会影响到继承他的子类
delete Person.sex;
m1.sex;//'man'