JavaScript 继承没有像我预期的那样工作

Question

pe.getName() 有效而 pe.getSalary() 无效的详细信息是什么？

var Employee = function(name) {
  this.name = name;
}

Employee.prototype.getName = function() {
  return this.name;
}

var PermanentEmployee = function(annualSalary) {
  this.annualSalary = annualSalary;
}

PermanentEmployee.prototype.getSalary = function() {
  return this.annualSalary;
}

var employee = new Employee("Mark");

PermanentEmployee.prototype = employee;

var pe = new PermanentEmployee(5000);

document.write(pe.getName());
document.write(pe.getSalary());

Answer 1

稍后在您的代码中执行此操作

PermanentEmployee.prototype = employee;

你可以覆盖这个

PermanentEmployee.prototype.getSalary = function()

试试这个:

function Employee(name) {
  this.name = name;
}

Employee.prototype.getName = function() {
  return this.name;
}
   
function PermanentEmployee(name, annualSalary) {
  Employee.call(this, name);  // calling parent's "constructor"
  this.annualSalary = annualSalary;
}
PermanentEmployee.prototype = Object.create(Employee.prototype); // setting "inheritance"
PermanentEmployee.prototype.getSalary = function() {
  return this.annualSalary;
}
var pe = new PermanentEmployee("Mark", 5000);

console.log(pe.getName());
console.log(pe.getSalary());