尝试学习Js并无法理解DOM元素为何不获取值:

var Car = function(loc) {
  var obj = Object.create(Car.prototype);
  obj.loc = loc;
  obj.move = move;
  return obj;
};

Car.prototype = {
    move : function() {
    this.loc++;
  }
};

var emy = Car(1);
emy.move();

document.getElementById("id").innerHTML = emy.loc;


因此,我创建了一个类构造函数及其原型对象,但是最后一行-document.getElementById("id").innerHTML = emy.loc;未被执行(除非我将其放在文件顶部)。这是为什么?

片段:

https://jsfiddle.net/awj6mf1b/

最佳答案

您尚未定义移动方式:

var Car = function(loc) {
  var obj = Object.create(Car.prototype);
  obj.loc = loc;
  obj.move = move;  // <<< Here
  return obj;
};


给出错误:

Uncaught ReferenceError: move is not defined
    at Car (VM52:51)
    at window.onload (VM52:61)


您可以通过在实例化过程中将函数放在对象中来解决此问题:

var Car = function(loc) {
  var obj = Object.create(Car.prototype);
  obj.loc = loc;
  obj.move = function() {
    this.loc++;
  }
  return obj;
};


或通过将函数正确添加到原型中:

var Car = function(loc) {
  var obj = Object.create(Car.prototype);
  obj.loc = loc;
  // Removed move from here
  return obj;
};

// This adds move to the cars prototype
Car.prototype.move = function() {
  this.loc++;
}

07-26 01:27