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 

  });

};