scrape amazon rankings

var casper = require('casper').create();
var all_links = [];
var top_kf8_picture_books_url = "http://www.amazon.com/Best-Sellers-Kindle-Store-Text-Pop-Up-Books/zgbs/digital-text/3381090011/#"
var index = 1;

function getLinks() {
    var links = document.querySelectorAll('.zg_itemImageImmersion a');
    return Array.prototype.map.call(links, function(e) {
        return e.getAttribute('href').trim();
    });
}

function logLinkElements(element, index, array) {
    rank = index+1;
    console.log("Rank " + rank + "=" + element);
}

function next20(index) {
    link = top_kf8_picture_books_url +index;
    this.echo( "Next 20 with "+ link);   
    this.thenOpen(link, function() {
        var wait_for_text = index * 19+".";
        this.echo( "Begin waiting for rank" + wait_for_text + "to appear");
        this.waitForText(wait_for_text, function() {
            this.echo('Found the rank.'+ wait_for_text);
            all_links = all_links.concat(this.evaluate( getLinks ));
            this.echo( "Ranks Collected so far"+ all_links.length );
            this.echo( all_links[all_links.length-1]);
            index += 1;
            if (all_links.length < 100 )
            {
                next20.call( this , index);
            }
            else
            {
                this.echo(all_links.length + ' links found:');
                all_links.forEach( logLinkElements );
                this.echo('completed').exit();
            }
        });
        
        this.echo(this.getTitle());
        
    });
}

casper.start();

casper.then(function() {
   next20.call( this, index );
});

casper.run();