Filter a <select> list with a <input type="text">.

filter-select-with-field.js

// depends on jquery

function filterSelectWithField(selectList, searchField) {
	selectList = $(selectList);
	searchField = $(searchField);
	options = selectList.find('option').clone();
	timer = null;
	
	function sanitize(str) {
		return $.trim(str).replace(/\s+/g, ' ').toLowerCase();
	}
	
	searchField.on('keyup', function(e) {
		var searchTerm = sanitize($(this).val());
		
		clearTimeout(timer);
		timer = setTimeout(function() {
			
			if(!searchTerm) {
				selectList.empty().append(options.clone());
				return;
			}
			
			matches = options.filter(function(idx) {
				return sanitize($(this).text()).indexOf(searchTerm) != -1;
			}).clone();
			
			selectList.empty().append(matches);

		}, 500);
		
	});
}