我有 3 個(gè)對(duì)象：科學(xué)、物理和數(shù)學(xué)。我希望最后兩個(gè)對(duì)象（物理和數(shù)學(xué)） 繼承科學(xué)的原型屬性。然而我希望數(shù)學(xué)和物理都更新繼承的屬性并定義它們的屬性。這已經(jīng)完成，但是當(dāng)我嘗試通過Physics實(shí)例訪問Science屬性和方法時(shí)，我總是得到未定義的信息。我的代碼可能有什么問題。function log(elem) {  return console.log(elem);}//create supertype => Sciencefunction Science() {}//define Science prototype propsScience.prototype = {  constructor: Science,  dificulty: "Variable",  universal: true,  type: "science",  name: "science",  hasSubFields() {    return true;  },};//create 2 sub fields : Mathematics and Physics to inherit props from Sciencefunction Mathematics(subField) {  this.subField = subField;}function Physics() {}//let mathematics & Physics inherit science propsMathematics.prototype = Object.create(Science.prototype);Physics.prototype = Object.create(Science.prototype);Physics.prototype.constructor = Physics;//over write Mathematics inherited props and physicsMathematics.prototype = {  constructor: Mathematics,  name: "Mathematics",  type: "Pure and applied Science",};Physics.prototype = {  name: "Physics",  dificulty: "80%",  type: "Physical Science",  subFields: ["Electricity", "Mechanics", "Sound", "Optics", "Waves"],};//make instance of Physicslet mechanics = new Physics();mechanics.name = "mechanics";mechanics.subFields = ["linear", "force", "force fileds"];log(mechanics.universal);