优化 carousel 移动端滑动切换

src/modules/carousel.js

@@ -331,13 +331,27 @@ layui.define(['jquery', 'lay'], function(exports){
     if(options.elem.data('haveEvents')) return;
     
     // 移入移出容器
-    options.elem.on('mouseenter', function(){
+    options.elem.on('mouseenter touchstart', function(){
       if (that.config.autoplay === 'always') return;
       clearInterval(that.timer);
-    }).on('mouseleave', function(){
+    }).on('mouseleave touchend', function(){
       if (that.config.autoplay === 'always') return;
       that.autoplay();
     });
+
+    var touchEl = options.elem;
+    var isVertical = options.anim === 'updown';
+    lay.touchSwipe(touchEl, {
+      onTouchEnd: function(e, state){
+        var duration = Date.now() - state.timeStart;
+        var delta = isVertical ? state.deltaY : state.deltaX;
+        var speed = delta / duration;
+        var shouldSwipe = Math.abs(speed) > 0.25 || Math.abs(delta) > touchEl[isVertical ? 'height' : 'width']() / 3;
+        if(shouldSwipe){
+          that.slide(delta > 0 ? '' : 'sub');
+        }
+      }
+    })
     
     options.elem.data('haveEvents', true);
   };

src/modules/lay.js

@@ -505,6 +505,110 @@
     }
   };
 
+  /**
+   * 检测是否支持 Passive Event Listeners
+   * 引用自 https://github.com/WICG/EventListenerOptions/blob/gh-pages/explainer.md
+   * @type {boolean}
+   */
+  lay.passiveSupported = function(){
+    var passiveSupported = false;
+    try {
+      var opts = Object.defineProperty({}, 'passive', {
+        get: function() {
+          passiveSupported = true;
+        }
+      });
+      window.addEventListener('test', null, opts);
+      window.removeEventListener('test', null, opts);
+    } catch (err) {}
+    return passiveSupported;
+  }();
+
+  /**
+   * 是否支持 touch 事件
+   */
+  lay.touchEventsSupported = function(){
+    return 'ontouchstart' in window;
+  };
+
+  /**
+   * @typedef touchSwipeState
+   * @prop {{x: number,y: number}} coordsStart - 初始坐标
+   * @prop {{x: number,y: number}} coordsEnd - 结束坐标
+   * @prop {number} deltaX - X 轴变化量
+   * @prop {number} deltaY - Y 轴变化量
+   * @prop {'none'|'right'|'left'|'up'|'down'} direction - 滑动方向
+   * @prop {Date} timeStart 开始时间
+   */
+  /**
+   * @callback touchSwipeCallback
+   * @param {TouchEvent} e 滑动事件
+   * @param {touchSwipeState} state 滑动相关的状态
+   */
+  /**
+   * 基于 touch 事件的触摸滑动
+   * @param {string | HTMLElement | JQuery} elem - HTML 元素
+   * @param {{onTouchStart?: touchSwipeCallback, onTouchMove?: touchSwipeCallback, onTouchEnd?: touchSwipeCallback}} opts - 配置项
+   */
+  lay.touchSwipe = function(elem, opts){
+    var options = opts
+    var targetElem = lay(elem)[0];
+
+    if(!targetElem || !lay.touchEventsSupported()) return;
+
+    var state = {
+      coordsStart: {x:0, y:0},
+      coordsEnd: {x:0, y:0},
+      deltaX: 0,
+      deltaY: 0,
+      direction:'none', // 'up','down','left','right','none
+      timeStart: null
+    }
+
+    var onStart = function(e){
+      if(e.touches.length !== 1) return;
+      bindEvents();
+      state.timeStart = Date.now();
+      state.coordsStart.x = state.coordsEnd.x = e.touches[0].clientX;
+      state.coordsStart.y = state.coordsEnd.y = e.touches[0].clientY;
+
+      options.onTouchStart && options.onTouchStart(e, state);
+    }
+
+    var onMove = function(e){
+      e.preventDefault();
+      state.coordsEnd.x = e.touches[0].clientX;
+      state.coordsEnd.y = e.touches[0].clientY;
+      state.deltaX = state.coordsStart.x - state.coordsEnd.x;
+      state.deltaY = state.coordsStart.y - state.coordsEnd.y;
+      if(Math.abs(state.deltaX) > Math.abs(state.deltaY)){
+        state.direction = state.deltaX > 0 ? 'left' : 'right';
+      }else{
+        state.direction = state.deltaY > 0 ? 'up' : 'down';
+      }
+      options.onTouchMove && options.onTouchMove(e, state);
+    }
+
+    var onEnd = function(e){
+      options.onTouchEnd && options.onTouchEnd(e, state);
+      unbindEvents();
+    }
+    
+    var bindEvents = function(){
+      targetElem.addEventListener('touchmove', onMove, lay.passiveSupported ? { passive: false} : false);
+      targetElem.addEventListener('touchend', onEnd);
+      targetElem.addEventListener('touchcancel', onEnd);
+    }
+
+    var unbindEvents = function(){
+      targetElem.removeEventListener('touchmove', onMove);
+      targetElem.removeEventListener('touchend', onEnd, lay.passiveSupported ? { passive: false} : false);
+      targetElem.removeEventListener('touchcancel', onEnd);
+    }
+
+    targetElem.addEventListener('touchstart', onStart);
+  }
+
 
   /*
    * lay 元素操作