JsonSearch($('#search_field').attr('value'), ['title', 'content']);
JsonSearch($('#search_field').val(), ['title', 'content']);
That seems to have fixed the problem. It was likely my fault for breaking it the first place. I've been adapting this site's engine from the excellent work of Simon Jodet and along with updating Bootstrap to version 3.1.1 I've also linked to the latest version of Jquery which may explain why .attr('value') doesn't work for me. At this point in time I have neither the patience or desire to find out why.