javascript - 为什么创建实例变量后标题没有正确设置？

Question

我正在尝试设置一个基本示例，我可以扩展我的主程序。我的问题是为什么标题不等于“HeyBARK”？我将 book 作为 bookTitles 类的一部分，所以设置的标题不应该自动添加树皮吗？

完成此操作后，我还需要引用我在原始作业中创建的大写方法。这个想法是，一旦像下面的代码片段那样设置了书名，我就会将该值传递到方法中并将其设置为等于返回结果。由于 setter 方法将接收整个对象，因此如何仅访问要修改的标题？

class bookTitle {
  constructor(title){
  this.title = title + "BARK";
}

// Everything in comments is part of the second paragraph in the 
// question, I will psuedo code it

// getter the object here to access its title

// use a setter to call my capitalization method to capitalize certain 
// words in the title

// title creator method that returns the modified value, will be called in setter

// cap method that purely caps the correct words, will be called within 
// title creator
}

var book = new bookTitle();
console.log(book); //title is undefinedBARK as expected
book.title = "Hey";
console.log(book); // currently returns Hey, not HeyBARK

如果它对我有帮助的话，这里是我当前工作解决方案的实际代码，前几天一位优秀的开发人员能够使其在隔离环境中工作，但现在我正在尝试修改它以 setter 方式工作。

titleCreator(string) {
        // Note that this isn't meant to be a fully fledged title creator, just designed to pass these specific tests
        var littleWords = ["and", "over", "the"]; // These are the words that we don't want to capitalize

        var self = this; // doesn't need to be here, just for syntax sugar, using this searches for things inside this class

        var modifiedString = string
        .split(' ') // Splits string into array of words, basically breaks up the sentence
        .map(function(word,index) {
            if (index == 0) {
                return self.capitalize(word); // capitalize the first word of the string
            } else if (littleWords.indexOf(word) == -1) {
                return self.capitalize(word); // capitalize any words that are not little, the -1 is returned by indexOf if it can't find the word in the array
            } else if (littleWords.indexOf(word) >= 0) {
                return word; // do not capitalize as this word is in the list of littleWords
            }
        })
        .join(' '); // Joins every element of an array into a string with a space inbetween each value. Basically you created a sentence from an array of words

        return modifiedString;

    }

    capitalize(word) {
        return word.charAt(0).toUpperCase() + word.slice(1);
        // This function just capitalizes the word given to it
    }

Answer 1

我认为您在这里误解了构造函数的概念。构造函数构建给定类的新实例，在本例中，您创建 BookTitle 类的实例。创建新实例后，构造函数不再对其具有任何权力。使用大写字母命名类并使用小写字母命名实例也是一个很好的做法。

要实现您想要的效果，您需要为您的属性指定 getter 和 setter，例如:

class BookTitle {
  constructor(title){
    this.title = title;
  }
  
  get title() {
    return this._title ;
  }
  
  set title(title) {
    this._title = title + 'BARK';
  }
}

let bookTitle = new BookTitle();
bookTitle.title = 'test';
console.log(bookTitle.title);