代理模式

1.本体

var Publication = new Interface('Publication', ['getIsbn', 'setIsbn', 'getTitle', 
  'setTitle', 'getAuthor', 'setAuthor', 'display']);
var Book = function(isbn, title, author) { ... } // implements Publication

/* Library interface. */

var Library = new Interface('Library', ['findBooks', 'checkoutBook', 'returnBook']);

/* PublicLibrary class. */

var PublicLibrary = function(books) { // implements Library
  this.catalog = {};
  for(var i = 0, len = books.length; i < len; i++) {
    this.catalog[books[i].getIsbn()] = { book: books[i], available: true };
  }
};
PublicLibrary.prototype = {
  findBooks: function(searchString) {
    var results = [];
    for(var isbn in this.catalog) {
      if(!this.catalog.hasOwnProperty(isbn)) continue;
      if(searchString.match(this.catalog[isbn].getTitle()) ||
          searchString.match(this.catalog[isbn].getAuthor())) {
        results.push(this.catalog[isbn]);
      }
    }
    return results;
  },
  checkoutBook: function(book) {
    var isbn = book.getIsbn();
    if(this.catalog[isbn]) {
      if(this.catalog[isbn].available) {
        this.catalog[isbn].available = false;
        return this.catalog[isbn];
      }
      else {
        throw new Error('PublicLibrary: book ' + book.getTitle() + 
          ' is not currently available.');
      }
    }
    else {
      throw new Error('PublicLibrary: book ' + book.getTitle() + ' not found.');
    }
  },
  returnBook: function(book) {
    var isbn = book.getIsbn();
    if(this.catalog[isbn]) {
      this.catalog[isbn].available = true;
    }
    else {
      throw new Error('PublicLibrary: book ' + book.getTitle() + ' not found.');
    }    
  }
};

2.实例代理

/* PublicLibraryProxy class, a useless proxy. */

var PublicLibraryProxy = function(catalog) { // implements Library
  this.library = new PublicLibrary(catalog);
};
PublicLibraryProxy.prototype = {
  findBooks: function(searchString) {
    return this.library.findBooks(searchString);
  },
  checkoutBook: function(book) {
    return this.library.checkoutBook(book);
  },
  returnBook: function(book) {
    return this.library.returnBook(book);
  }
};

3.虚拟代理

/* PublicLibraryVirtualProxy class. */

var PublicLibraryVirtualProxy = function(catalog) { // implements Library
  this.library = null;
  this.catalog = catalog; // Store the argument to the constructor.
};
PublicLibraryVirtualProxy.prototype = {
  _initializeLibrary: function() {
    if(this.library === null) {
      this.library = new PublicLibrary(this.catalog);
    }
  },
  findBooks: function(searchString) {
    this._initializeLibrary();
    return this.library.findBooks(searchString);
  },
  checkoutBook: function(book) {
    this._initializeLibrary();
    return this.library.checkoutBook(book);
  },
  returnBook: function(book) {
    this._initializeLibrary();
    return this.library.returnBook(book);
  }
};

 4.远程模式

/* WebserviceProxy class */

var WebserviceProxy = function() {
  this.xhrHandler = XhrManager.createXhrHandler();
};
WebserviceProxy.prototype = {  
  _xhrFailure: function(statusCode) {
    throw new Error('StatsProxy: Asynchronous request for stats failed.');
  },
  _fetchData: function(url, dataCallback, getVars) {
    var that = this;
    var callback = { 
      success: function(responseText) {
        var obj = eval('(' + responseText + ')');
        dataCallback(obj);
      }, 
      failure: that._xhrFailure
    };
    
    var getVarArray = [];
    for(varName in getVars) {
      getVarArray.push(varName + '=' + getVars[varName]);
    }
    if(getVarArray.length > 0) {
      url = url + '?' + getVarArray.join('&');
    }
    
    xhrHandler.request('GET', url, callback);    
  }
};

/* StatsProxy class, using WebserviceProxy. */

var StatsProxy = function() {}; // implements PageStats
extend(StatsProxy, WebserviceProxy);

/* Implement the needed methods. */

StatsProxy.prototype.getPageviews = function(callback, startDate, endDate, 
    page) {
  this._fetchData('/stats/getPageviews/', callback, { 
    'startDate': startDate, 
    'endDate': endDate, 
    'page': page 
  });
};
StatsProxy.prototype.getUniques = function(callback, startDate, endDate, 
    page) {
  this._fetchData('/stats/getUniques/', callback, { 
    'startDate': startDate, 
    'endDate': endDate, 
    'page': page 
  });
};
StatsProxy.prototype.getBrowserShare = function(callback, startDate, endDate, 
   page) {
  this._fetchData('/stats/getBrowserShare/', callback, { 
    'startDate': startDate, 
    'endDate': endDate, 
    'page': page 
  });
};
StatsProxy.prototype.getTopSearchTerms = function(callback, startDate, 
    endDate, page) {
  this._fetchData('/stats/getTopSearchTerms/', callback, { 
    'startDate': startDate, 
    'endDate': endDate, 
    'page': page 
  });
};
StatsProxy.prototype.getMostVisitedPages = function(callback, startDate, 
    endDate) {
  this._fetchData('/stats/getMostVisitedPages/', callback, { 
    'startDate': startDate, 
    'endDate': endDate 
  });
};