我在
JavaScript中不明白什么时候使用单词“prototype”,而不使用简单的“dot”符号而没有单词“prototype”.有人可以看这些代码块,并帮助我了解什么时候想要使用另一个？
与“原型”：
function employee(name,jobtitle)
{
this.name=name;
this.jobtitle=jobtitle;
}
var fred=new employee("Fred Flintstone","Caveman");
employee.prototype.salary=null;
fred.salary=20000;
console.log(fred.salary);
没有“原型”：
function employee(name,jobtitle,salary)
{
this.name=name;
this.jobtitle=jobtitle;
this.salary=salary;
}
var fred=new employee("Fred Flintstone","Caveman",20000);
console.log(fred.salary);
解决方法
JavaScript对象具有指向另一个对象的指针的属性.这个指针是对象的原型.对象实例默认共享相同的原型：
function Employee(name){
this.name = name;
}
Employee.prototype.company = "IBM";
Employee.prototype.who = function(){
console.log("My name is",this.name,"I work for",this.company);
}
var bob = new Employee('Bob');
var jim = new Employee('Jim');
// bob and jim are seperate objects,but each is linked to the same 'prototype' object.
jim.who(); // jim doesn't have a property called 'who',so it falls back to it's 'prototype',where who exists
// My name is Jim I work for IBM
bob.who();
// My name is Bob I work for IBM
// Bob leaves IBM for Microsoft
bob.company = "Microsoft"; // bob Now has a property called 'company'. The value of which is 'Microsoft',which overrides bob's prototype property of the same name.
bob.who();
// My name is Bob I work for Microsoft
Employee.prototype.company = 'Facebook';
jim.who();
// My name is Jim I work for Facebook
bob.who(); // Bob is not affected by the change.
// My name is Bob I work for Microsoft
delete bob.company;
bob.who(); // bob no longer has it's own property 'company',so like jim,it drops down to the prototype object.
// My name is Bob I work for Facebook