Getting the book list from tag

We do the intersection based only on ISBN because the simple string value can make best use of the Lo-Dash’s methods.

1data.findBooksByTags = function(tags) {
2  var isbns = this.allIsbns(); // all books by default
3  _.forEach(tags, function(tag){ // loop all tags
4    var isbnsFromTag = data.storage.loadList("tag:" + tag); // get the ISBN list from the tag
5    isbns = _.intersection(isbns, isbnsFromTag); // intersect with the result.
6  });
7  return this.findBooksByIsbns(isbns); // get back the book list from ISBNs.
8}

We need an array of all book ISBNs. This can be done by list all books and retrieve the ISBN in each book. You may think of a for-loop statement, but the map function can help.

1// return all ISBNs of each book in book list.
2data.allIsbns = function() {
3  return _.map(this.books, function(book){
4    return book.isbn;
5  })
6}

Since the collection manipulation is based on ISBNs, the last thing we need to do is retrieve the book list from the ISBNs.

 1// isbns should be array
 2data.findBooksByIsbns = function(isbns) {
 3  var result = [];
 4  for(var i=0, len=data.books.length; i<len; i++) {
 5    var book = data.books[i];
 6    if (_.contains(isbns, book.isbn)) {
 7      result.push(book);
 8    }
 9  }
10  return result;
11};

What’s next? We’re going to take a look at “Render book list with argument”.

◀ Adding the ISBNs to tag data Render book list with argument ▶

makzan.

Getting the book list from tag

Makzan | Mobile web app dev with phonegap | Table of Content