闭包练习

    var Book=(function(){
        var numOfBooks=0;
        function checkIsbn(isbn){
            
        }
        return function(isbn,title,author){
            var _isbn,_title,_author;

            this.setIsbn=function(isbn){
                _isbn=isbn;
            }
            this.getIsbn=function(){
                return _isbn;
            }
            numOfBooks++;
            if(numOfBooks>50){
                throw new Error('只能调用50次')
            };
            this.setIsbn(isbn);
        }
    })()
    Book.convertToTitleCase=function(inputSting){
        console.log(inputSting);
    }
    Book.prototype={
        display:function(){
            console.log("display")
        }
    };

    var c=new Book();
    
    c.setIsbn("10080");
    console.log(c.getIsbn());