javascript 代理模式

通过图来讲解什么是惰性代理(第二个案例)

普通代理模式(用处不大,基本不用,主要做案例说明代理模式是什么)

   /*
        * 普通代理模式
        * */
        //图书类
        var Book = function (bid,bName,bPrice) {
            this.bid = bid;
            this.bName = bName;
            this.bPrice = bPrice;
        }      
        //目标类        
        var BookShop = (function () {
            var books = {};
            return function (bks) {
                if(typeof bks == "object"){
                    books = bks;
                };
                //加书
                this.addBook = function (book) {
                    books[book.bid] = book;
                };
                //找书
                this.findBook =function (bid) {
                    if(books[bid]){
                        return books[bid];
                    }else{
                        return null;
                    }
                };
                //还书
                this.returnBook=function (book) {
                    this.addBook(book);
                };
                //借书
                this.checkBook=function (bid) {
                    var book = this.findBook(bid);
                    return book;
                }
            }
        })();

        //普通代理
        var proxyBookShop = function (bks) {
            var obj = new BookShop(bks);
            //加书
            this.addBook = function (book) {
               obj.addBook(book);
            };
            //找书
            this.findBook =function (bid) {
                return obj.findBook(bid);
            };
            //还书
            this.returnBook=function (book) {
               obj.returnBook(book)
            };
            //借书
            this.checkBook=function (bid) {
               return obj.checkBook(bid);
            }
        }
        var proxy = new proxyBookShop({
            "001":new Book('001','js',85),
            "002":new Book('002','html',30),
            "003":new Book('003','css',45),
        });
        console.log(proxy.checkBook("001").bName);

惰性代理模式

 /*
        * 惰性代理
        *
        * */

        //图书类
        var Book = function (bid,bName,bPrice) {
            this.bid = bid;
            this.bName = bName;
            this.bPrice = bPrice;
        }

        //目标类

        var BookShop = (function () {
            var books = {};
            return function (bks) {
                if(typeof bks == "object"){
                    books = bks;
                };
                //加书
                this.addBook = function (book) {
                    books[book.bid] = book;
                };
                //找书
                this.findBook =function (bid) {
                    if(books[bid]){
                        return books[bid];
                    }else{
                        return null;
                    }
                };
                //还书
                this.returnBook=function (book) {
                    this.addBook(book);
                };
                //借书
                this.checkBook=function (bid) {
                    var book = this.findBook(bid);
                    return book;
                }
            }
        })();
        

        var proxyBookShop = function (bks) {

            var obj =null;
            this._init = function () {
                console.log("在调用内部方法时,初始化本类");
                obj = new BookShop(bks);

            }
            //加书
            this.addBook = function (book) {
                this._init();
                obj.addBook(book);
            };
            //找书
            this.findBook =function (bid) {
                this._init();
                return obj.findBook(bid);
            };
            //还书
            this.returnBook=function (book) {
                this._init();
                obj.returnBook(book)
            };
            //借书
            this.checkBook=function (bid) {
                this._init();
                return obj.checkBook(bid);
            }
        };
        var proxy = new proxyBookShop({
            "001":new Book('001','js',85),
            "002":new Book('002','html',30),
            "003":new Book('003','css',45),
        });

        console.log(proxy.checkBook("001").bName);