ES6 Class 转为 ES5

class Test {
  constructor(name, age) {
    this.name = name;
    this.age = age;
  }

  getName() {
    console.log(this.name);
  }
}

基础转换

'use strict'; // es6 class 在严格模式下执行

function Test(name, age) {
  this.name = name;
  this.age = age;
}

Test.prototype.getName = function () {
  console.log(this.name);
};

class 只能使用 new 调用

判断函数调用的方式

"use strict"; // es6 class 在严格模式下执行

function Test(name, age) {
  // 验证this的指向
  const isCalledWithNew = this instanceof Test;
  if (!isCalledWithNew) {
    throw new TypeError(
      "Class constructor Test cannot be invoked without 'new'"
    );
  }
  this.name = name;
  this.age = age;
}

Test.prototype.getName = function () {
  console.log(this.name);
};

class 方法成员不可被枚举

示例中 class 的方法 getName 不可枚举

'use strict'; // es6 class 在严格模式下执行

function Test(name, age) {
  // 验证this的指向
  const isCalledWithNew = this instanceof Test;
  if (!isCalledWithNew) {
    throw new TypeError("Class constructor Test cannot be invoked without 'new'");
  }
  this.name = name;
  this.age = age;
}

Object.defineProperty(Test.prototype, "getName", {  
  value: function () {                              
    console.log(this.name);                         
  },                                                
  enumerable: false,                                
});                                                 

Test.prototype.getName = function () {  
  console.log(this.name);               
};                                      

class 方法成员不能使用 new 调用

"use strict"; // es6 class 在严格模式下执行

function Test(name, age) {
  // 验证this的指向
  const isCalledWithNew = this instanceof Test;
  if (!isCalledWithNew) {
    throw new TypeError(
      "Class constructor Test cannot be invoked without 'new'"
    );
  }
  this.name = name;
  this.age = age;
}

Object.defineProperty(Test.prototype, "getName", {
  value: function () {
    // 不能使用 new 调用
    if (!(this instanceof Test)) {       
      throw new TypeError("instance.getName is not a constructor"); 
    }                                    
    console.log(this.name);
  },
  enumerable: false,
});