data.chinahighlights.com/js/jquery.combobox-0.5.js

(function($) {
  $.fn.combobox = function(options) {
    var defaults = {
      maxLength: 5,
      source: [],
      onSelect: function() {}
    };
    var settings = $.extend(defaults, options);
    var $inputElement = this;
    $inputElement.wrap("<span style='position: relative; display: block;'>");
    var $divHtml =
      $("<div class='combobox' style='position: absolute; top: 100%; left: 0px; z-index: 100; display: none;'></div>");
    var $ulHtml =
      $("<ul class='list-unstyled' style='width: 100%;text-align: left;'></ul>");
    var dataset = settings.source;
    for (var rowNum = 0; rowNum < dataset.length; rowNum++) {
      var data = dataset[rowNum];
      var $liHtml = $("<li class='combobox-item' item-value='" + data.value + "'>" + data.text + "</li>");

      if (data.disable) {
        $liHtml.removeClass("combobox-item");
      } else {
        $liHtml.click(function() {
          $inputElement.val($(this).attr("item-value"));
          if ( $.isFunction( settings.onSelect ) ) {
            settings.onSelect.call(this);
          }
        });
      }

      $liHtml.appendTo($ulHtml);
    }

    $ulHtml.appendTo($divHtml);
    $inputElement.after($divHtml);
    $inputElement.focus(function() {
      $divHtml.show('fast');
    }).blur(function() {
      $divHtml.fadeOut();
    });

    $inputElement.keydown(function(event) {
      var keyCode = event.keyCode || event.which;
      if (keyCode == 8 || keyCode == 46 ||
        (keyCode >= 37 && keyCode <= 40)) {
        return true;
      } else if ((keyCode >= 48 && keyCode <= 57) ||
        (keyCode >= 96 && keyCode <= 105)) {
        if ($inputElement.val().length < settings.maxLength) {
          return true;
        } else {
          return false;
        }
      } else {
        return false;
      }
    }).blur(function() {
      var str = $inputElement.val();

      if (str.length > settings.maxLength) {
        str = str.substring(0, settings.maxLength);
      }

      if (/^\d+$/.test(str)) {
        $inputElement.val(str);
      } else {
        $inputElement.val("");
      }
      if ( $.isFunction( settings.onSelect ) ) {
        settings.onSelect.call(this);
      }
    }).focus(function() {
      this.style.imeMode = 'disabled';
    });

    return this;
  };
})(jQuery);