js深入研究之初始化验证

<script type="text/javascript">
var Book = function(isbn, title, author) {
  if(!this.checkIsbn(isbn)){
      throw new Error('Book: Invalid ISBN.');
  } 
  this.isbn = isbn;
  this.title = title || 'No title specified';
  this.author = author || 'No author specified';
}

Book.prototype = {
  checkIsbn: function(isbn) {
    if(isbn == undefined || typeof isbn != 'string') {
      return false;
    }
    return true; // All tests passed.
  },
  display: function() {
    alert("isbn:"+this.isbn+" title:"+this.title+" author:"+this.author);
  }
};

var theHobbit = new Book('0-395-07122-4', 'The Hobbit', 'J. R. R. Tolkein');
theHobbit.display(); // Outputs the data by creating and populating an HTML element.

</script>

对isbn进行验证。是否定义，是否为字符串等等。对title进行判断，设置默认。

另一种实现方式

<script type="text/javascript">
/* 出版 interface. */
/* var Publication = new Interface('Publication', ['getIsbn', 'setIsbn', 'getTitle',
  'setTitle', 'getAuthor', 'setAuthor', 'display']); */

var Book = function(isbn, title, author) { // implements Publication
  this.setIsbn(isbn);
  this.setTitle(title);
  this.setAuthor(author);
}

Book.prototype = {
  checkIsbn: function(isbn) {
    if(isbn == undefined || typeof isbn != 'string') {
      return false;
    }
    return true; // All tests passed.
  },
  getIsbn: function() {
    return this.isbn;
  },
  setIsbn: function(isbn) {
    if(!this.checkIsbn(isbn)) throw new Error('Book: Invalid ISBN.');
    this.isbn = isbn;
  },

  getTitle: function() {
    return this.title;
  },
  setTitle: function(title) {
    this.title = title || 'No title specified';
  },

  getAuthor: function() {
    return this.author;
  },
  setAuthor: function(author) {
    this.author = author || 'No author specified';
  },

  display: function() {
    alert("isbn:"+this.isbn+" title:"+this.title+" author:"+this.author);
  }
};


var theHobbit = new Book('0-395-07122-4', '', 'J. R. R. Tolkein');
theHobbit.display(); // Outputs the data by creating and populating an HTML element.

</script>

接口实现，参考接口，定义了好多方法。

内部方法命名加_，例如这个检测的方法 _checkIsbn

<script type="text/javascript">
/* 出版 interface. */
/* var Publication = new Interface('Publication', ['getIsbn', 'setIsbn', 'getTitle',
  'setTitle', 'getAuthor', 'setAuthor', 'display']); */

var Book = function(isbn, title, author) { // implements Publication
  this.setIsbn(isbn);
  this.setTitle(title);
  this.setAuthor(author);
}

Book.prototype = {
  _checkIsbn: function(isbn) {
    if(isbn == undefined || typeof isbn != 'string') {
      return false;
    }
    return true; // All tests passed.
  },
  getIsbn: function() {
    return this.isbn;
  },
  setIsbn: function(isbn) {
    if(!this._checkIsbn(isbn)) throw new Error('Book: Invalid ISBN.');
    this.isbn = isbn;
  },

  getTitle: function() {
    return this.title;
  },
  setTitle: function(title) {
    this.title = title || 'No title specified';
  },

  getAuthor: function() {
    return this.author;
  },
  setAuthor: function(author) {
    this.author = author || 'No author specified';
  },

  display: function() {
    alert("isbn:"+this.isbn+" title:"+this.title+" author:"+this.author);
  }
};


//var theHobbit = new Book(123, '', 'J. R. R. Tolkein'); // 非字符串抛出异常
var theHobbit = new Book('1990-78sd-1092', '', 'J. R. R. Tolkein'); 
theHobbit.display(); // Outputs the data by creating and populating an HTML element.


</script>