input模拟输入下拉框

　   功能点：

　　　　输入、下拉选择、根据输入内容模糊检索、键盘上下键选择

　　实现思路：

　　　　显示隐藏：

　　　　　　input获取焦点显示，失去焦点隐藏

　　　　下拉选择：

　　　　　　以父元素为基准，通过绝对定位定位至input输入下方

　　　　模糊检索：

　　　　　　监听输入数据的变化，过滤符合要求的数据

　　　　键盘上下选择：

　　　　　　监听input的键盘事件，判断keycode值，再触发上下键时，动态计算滚动条滚动的距离

　　　　控制事件触发频率，采用函数节流

　　具体实现过程：

　　　　节流函数：

 function throttle(func, wait, options) {//函数节流
         var context, args, result;
         var timeout = null;
         var previous = 0;
         if (!options) options = {};
         var later = function() {
             previous = options.leading === false ? 0 : new Date().getTime();
             timeout = null;
             result = func.apply(context, args);
             if (!timeout) context = args = null;
         };
         return function() {
             var now = new Date().getTime();
             if (!previous && options.leading === false) previous = now;
             var remaining = wait - (now - previous);
             context = this;
             args = arguments;
             if (remaining <= 0 || remaining > wait) {
                 if (timeout) {
                     clearTimeout(timeout);
                     timeout = null;
                 }
                 previous = now;
                 result = func.apply(context, args);
                 if (!timeout) context = args = null;
             } else if (!timeout && options.trailing !== false) {
                 timeout = setTimeout(later, remaining);
             }
             return result;
         }
     }

功能代码：

 xxx.directive('inputAndSelect', function ($timeout) {
     return {
       restrict: 'AE',
       replace: true,
       require: 'ngModel',
       scope: {
         'ngModel': '=',
         'data': '@',
         'callback': '&'
       },
       template: '<div class="select-box">' +
         ' <input type="text" ng-focus="inputOnFocus($event)" ng-blur="inputOnBlur()"' +
         '      ng-model="ngModel" style="z-index: 10;" class="form-control huowu-input"><span class="arrow-down" style="display:inline-block;width: 12px;height: 8px;right: 14px;' +
         '   border-left: 6px solid transparent;\n' +
         '    border-right: 6px solid transparent;\n' +
         '    border-top: 8px solid #818181;"></span>' +
         '   <div class="select-box-container" style="z-index: 999;background-color: #fff;" ng-show="showSelect">' +
         '     <div class="select-box-item" ng-click="selectInputItem(item)" ng-repeat="item in dataList">{{item}}</div></div>' +
         '</div>',
       link: function(scope, element, attrs) {
         //显示/隐藏下拉列表
         scope.showSelect = false;
         scope.dataList = [];
         scope.selectIndex = -1;
         var eleInput = element.find('input');
         eleInput.attr('id', attrs.id);
         //input获取焦点
         eleInput.unbind('focus').bind('focus',function() {
           scope.showSelect = true;
           scope.dataList = JSON.parse(scope.data);
           element.find('.select-box-container .select-box-item').removeClass('option-active');
           $timeout(function () {
             element.find('.select-box-container').scrollTop(0);
           }, 0);
           if (scope.ngModel) {
             scope.dataList = scope.dataList.filter(function(vv) {
               return vv.indexOf(scope.ngModel) !== -1;
             })
           }
           if(attrs.callback) {
             scope.$parent[attrs.callback]();
           }
         });
         //选择输入项
         scope.selectInputItem = function(item) {
           scope.ngModel = item;
           scope.showSelect = false;
         };

         //input失去焦点
         scope.inputOnBlur = function() {
           $timeout(function() {
             scope.selectIndex = -1;
             scope.showSelect = false;
           }, 200)
         };
         //监听输入数据的变化
         scope.$watch('ngModel', function(newVal) {
           if(!scope.data) return;
           var items = JSON.parse(scope.data);
           if (!newVal && typeof newVal === 'string') {
             scope.dataList = items;
           } else {
             scope.dataList = items.filter(function(vv) {
               return vv.indexOf(newVal) !== -1;
             })
           }
         });
         //监听键盘按下事件
         eleInput.unbind('keydown').bind('keydown', throttle(function(e) {
           //keycode 38 up 40 down
           var items = element.find('.select-box-container .select-box-item');
           var $container = element.find('.select-box-container');
           var keycode = e.keyCode;
           if (keycode === 40) {
             //按键向下
             scope.selectIndex++;
             scope.selectIndex = scope.selectIndex > scope.dataList.length - 1 ? 0 : scope.selectIndex;
           } else if (keycode === 38) {
             //按键向上
             scope.selectIndex--;
             scope.selectIndex = scope.selectIndex < 0 ? scope.dataList.length - 1 : scope.selectIndex;
           } else if (keycode === 13) {
             if (scope.selectIndex !== -1) {
               scope.ngModel = scope.dataList[scope.selectIndex];
               scope.showSelect = false;
             }
             element.find('input').blur();
           }else {
             return;
           }
           items.removeClass('option-active');
           $(items[scope.selectIndex]).addClass('option-active');
           if(scope.selectIndex === 0) {
             $container.scrollTop(0);
           }
           $container.scrollTop(scope.selectIndex*25);
         }, 50));
       }
     }
   })

　　　效果图：