如何在对象中找到特定项目不是javascript中的函数

Question

I have the below code to Manage a collection of Books.

var Book = function(title,pages,priority){
    this.title = title;
    this.pages = pages;
    this.priority = priority;
    this.GetMaxmimumDays=function(){ 
        var effortCalculator = new EffortCalculator(this.pages);
        return effortCalculator.CalculateDays();
    }
};
var BooksCollection = (function(){
    var books=[];
    return {
        Add:function(book){
            books.push(book);
        },
        Remove:function(title){
            for(var i=0;i<books.length;i++){
                if(books[i]["title"]==title){
                    books[i]["title"]=null;
                }
            }
        },
        Print:function(){
            for(var i=0;i<books.length;i++){
                var itemText="";
                for(item in books[i]){
                    itemText=itemText+""+item+":"+books[i][item];
                }
                alert("item"+itemText); /** itemText prints the string includes the function definition. **/
            }
        },
        Count:books.length,
        SortByPriority:function(){

        }
    };
})();

in the above code BooksCollection.Print() prints everyItem and everyProperty in the collection. however the book instance have got function member. The same is getting printed in alert.

I wrapped around the Print() as below to hide out the function being printed in the output.

        Print:function(){
            for(var i=0;i<books.length;i++){
                var itemText="";
                for(item in books[i]){
                    if(!(item instanceof Function)){
                        itemText=itemText+""+item+":"+books[i][item];
                    }
                }
                alert("item"+itemText);
            }
        }

but things are still negative. I tried (typeof(item)==="Function") but the typeof(item) still reads "String".

I wonder the suspicious act of typeof and instanceOf keywords.

you can find a fiddle over here. http://jsfiddle.net/saravanakumarrc/rDEnt/40/

Please help me out to find the solution.

Answer 1

In your case, typeof item will always be a string - its the key to the property of the Book being enumerated.

What you want to test is the value of that item, so you want typeof books[i][item] :

 for(item in books[i]){
     if(typeof books[i][item] != 'function'){
         itemText=itemText+""+item+":"+books[i][item]+ '\r\n';
     }
 }

Live example: http://jsfiddle.net/kDHfU/