js深入研究之神奇的匿名函数类生成方式

<script type="text/javascript">
var Book = (function() {

// 私有静态属性
var numOfBooks = 0;

// 私有静态方法
function checkIsbn(isbn) {
if(isbn == undefined || typeof isbn != 'string') {
return false;
}
return true;
}

// 返回构造函数
return function(newIsbn, newTitle, newAuthor) { // implements Publication

// 私有属性
var isbn, title, author;

// 特权方法
this.getIsbn = function() {
return isbn;
};
this.setIsbn = function(newIsbn) {
if(!checkIsbn(newIsbn)) throw new Error('Book: Invalid ISBN.');
isbn = newIsbn;
};

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

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

// 控制对象数目，构造函数
numOfBooks++; // Keep track of how many Books have been instantiated
// with the private static attribute.
if(numOfBooks > 5) throw new Error('Book: Only 5 instances of Book can be '
+ 'created.');

this.setIsbn(newIsbn);
this.setTitle(newTitle);
this.setAuthor(newAuthor);
}
})();

// 公有静态方法
Book.convertToTitleCase = function(inputString) {
alert('convertToTitleCase');
};

// 公有非特权方法
Book.prototype = {
display: function() {
alert("isbn:"+this.getIsbn()+" title:"+this.getTitle()+" author:"+this.getAuthor());
}
};
//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();
//theHobbit.convertToTitleCase(); // Uncaught TypeError: Object #<Object> has no method 'convertToTitleCase'
Book.convertToTitleCase();  // 输出convertToTitleCase

var theHobbit2 = new Book('1990-78sd-1092', '', 'J. R. R. Tolkein');
theHobbit2.display();

var theHobbit3 = new Book('1990-78sd-1092', '', 'J. R. R. Tolkein');
theHobbit3.display();

var theHobbit4 = new Book('1990-78sd-1092', '', 'J. R. R. Tolkein');
theHobbit4.display();

var theHobbit5 = new Book('1990-78sd-1092', '', 'J. R. R. Tolkein');
theHobbit5.display();

var theHobbit6 = new Book('1990-78sd-1092', '', 'J. R. R. Tolkein');
theHobbit6.display(); // Uncaught Error: Book: Only 5 instances of Book can be created.

</script>