javascript - 无法在构造函数原型(prototype)中调用 'this'

Question

这个问题已经有答案了:

How can I maintain control of the this keyword when extending prototypes in jQuery? [duplicate] (3 个回答)

已关闭 7 年前。

我无法弄清楚为什么我无法在 Game 构造函数的原型(prototype)中使用“this.count”而不会出现 NaN 或未定义。每当用户正确回答四个问题之一时，我就用它来跟踪分数。

我曾假设，一旦在构造函数中声明了一个属性，它就可以在其任何原型(prototype)中使用？预先感谢您。

var questions = [
  {question: "What programming language does the library 'jQuery' belongs to?",
  answer: "JAVASCRIPT"},
  {question: "What programming language does 'Sass' builds upon?",
  answer: "CSS"},
  {question: "How do you abbreviate Hyper Text Markup Language?",
  answer: "HTML"},
  {question: "What company does the framework 'Bootstrap' belong to?",
  answer: "TWITTER"}
];

var Game = function(array) {
  this.array = array;
  this.count = 0;   // this.count is set to 0 //
}

var guess = new Game(questions);

Game.prototype.play = function() {
  console.dir(this.array);
  console.dir(this.count);
  $('button').click(function() {
    for (var i = 0; i < this.array.length; i++) {
        var newGuess = prompt(this.array[i].question).toUpperCase();
        if (newGuess === this.array[i].answer) {
            ++this.count;    // Problem happens here //
            console.log(this.count);
        } else {
            alert('Incorrect.');
        }
    }
    alert('You answered ' + this.count + ' out of 4 correct.');
  });
}
guess.play();

Answer 1

在匿名函数内部，“this”引用的是匿名函数本身，而不是 Game。添加:

    var self = this;

在 .click(...) 之前并将“this”替换为“self”。