JavaScript对象初始化与ISBN校验实现详解

JavaScript对象初始化与ISBN校验实现详解

本文通过具体实例介绍了JavaScript中初始化验证的实现方法，供读者参考学习。

<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>

主要对ISBN字段进行验证，检查其是否已定义且类型为字符串。同时对title字段进行判断，若未提供则设置默认值。

以下是另一种实现方式的代码示例。

<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>

该方案参考了接口模式进行实现，定义了多个相关方法以规范对象行为。

内部辅助方法采用下划线前缀命名，例如用于检测ISBN有效性的私有方法 _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>

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希望本文所述对大家JavaScript程序设计有所帮助。