Why is this Javascript much *slower* than its jQuery equivalent?

Question

I have a HTML list of about 500 items and a "filter" box above it. I started by using jQuery to filter the list when I typed a letter (timing code added later):

$('#filter').keyup( function() {
    var jqStart = (new Date).getTime();

    var search = $(this).val().toLowerCase();
    var $list = $('ul.ablist > li');

    $list.each( function() {
        if ( $(this).text().toLowerCase().indexOf(search) === -1 )
            $(this).hide();
        else
            $(this).show();
    } );

    console.log('Time: ' + ((new Date).getTime() - jqStart));
} );

However, there was a couple of seconds delay after typing each letter (particularly the first letter). So I thought it may be slightly quicker if I used plain Javascript (I read recently that jQuery's each function is particularly slow). Here's my JS equivalent:

document.getElementById('filter').addEventListener( 'keyup', function () {
    var jsStart = (new Date).getTime();

    var search = this.value.toLowerCase();
    var list = document.querySelectorAll('ul.ablist > li');
    for ( var i = 0; i < list.length; i++ )
    {
        if ( list[i].innerText.toLowerCase().indexOf(search) === -1 )
            list[i].style.display = 'none';
        else
            list[i].style.display = 'block';
    }

    console.log('Time: ' + ((new Date).getTime() - jsStart));
}, false );

To my surprise however, the plain Javascript is up to 10 times slower than the jQuery equivalent. The jQuery version takes around 2-3 seconds to filter on each letter, while the Javascript version takes 17+ seconds! I'm using Google Chrome on Ubuntu Linux.

This isn't for anything really important so it doesn't need to be super efficient. But am I doing something really dumb with my Javascript here?

Answer 1

You could try using textContent instead of innerText , I think it should be faster. Also timing the list-generation and loop separately would tell if there is problem in list-generation.

Answer 2

Another best practice for javascript speed is caching the list.length in a variable and calling the variable like:

l = list.length;
for (var i=0;i<l;i++):{ code here}

And maybe timing with jsperf would be better.