JS class语法糖的深入剖析

class Person {
  constructor(firstName, lastName) {
    this.firstName = firstName;
    this.lastName = lastName;
  } // Person.constructor
  get FullName () {
    return this.firstName + " " + this.lastName;
  }
} // Person
class Employee extends Person {
  #salary;
  constructor(firstName, lastName, salary) {
    super(firstName, lastName);
    this.salary = salary;
  }
  get salary() {
    return this.#salary;
  }
  set salary(salary) {
    this.#salary = salary;
    console.log("Salary changed for " + this.fullName + " : $" + this.salary);
  }
} // Employee

const Person = {
  set givenName(givenName) {
    this._givenName = givenName;
  },
  set familyName(familyName) {
    this._familyName = familyName;
  },
  get fullName() {
    return `${this._givenName} ${this._familyName}`;
  }
};
const test = Person; // 这里假设用 对象 模拟 类
test.givenName = "Joe";
test.familyName = "Martinez";
console.log("test.fullName", test.fullName); // Joe Martinez
console.log("test.givenName", test.givenName); // undefined
console.log("test._givenName", test._givenName); // Joe

class Cash {
  constructor() {
    this.total = 0;
  }
  add(amount) {
    this.total += amount;
    if (this.total < 0) this.total = 0;
  }
} // Cash
class Nickles extends Cash {
  add(amount) {
    super.add(amount * 5);
  }
} // Nickles

const Cash = function() {
  this.total = 0;
}; // Cash
Cash.prototype = {
  add : function(amount) {
    this.total += amount;
    if (this.total < 0) this.total = 0;
  }
}; // Cash.prototype
const Nickles = function() {
  Object.assign(this, new Cash());
  this.add = function(amount) {
    Cash.add.apply(this, amount);
  };
} // Nickles