利用闭包判断Dom元素和滚动条的方向

本文收集整理自网上。

一，判断滚动条的方向，利用闭包首先保存滚动条的位置，然后当滚动时候不断更新滚动初始值，然后通过差指判断方向

 1     function scroll(fn) {
 2         //利用闭包判断滚动条滚动的方向
 3         var beforeScrollTop = document.body.scrollTop,
 4             fn = fn || function() {};
 5         window.addEventListener("scroll", function() {
 6             var afterScrollTop = document.body.scrollTop,
 7                 delta = afterScrollTop - beforeScrollTop;
 8             if (delta === 0) return false;
 9             fn(delta > 0 ? "down" : "up");
10             beforeScrollTop = afterScrollTop;
11         }, false);
12     }
13     scroll(function(direction) { console.log(direction) });

二，判断鼠标的移动方向

 1     function direction() {
 2         var lastX = null,
 3             lastY = null;
 4         window.addEventListener("mousemove", function(event) {
 5             var curX = event.clientX,
 6                 curY = event.clientY,
 7                 direction = '';
 8             // console.info(event);
 9             // console.info(event.clientX);
10             // console.info(event.clientY);
11             // 初始化坐标
12             if (lastX == null || lastY == null) {
13                 lastX = curX;
14                 lastY = curY;
15                 return;
16             }
17             if (curX > lastX) {
18                 direction += 'X右,';
19             } else if (curX < lastX) {
20                 direction += 'X左,';
21             }
22             if (curY > lastY) {
23                 direction += 'Y下';
24             } else if (curY < lastY) {
25                 direction += 'Y上';
26             }
27             lastX = curX;
28             lastY = curY;
29             //console.info(direction);
30             document.getElementById("test").innerText = direction;
31         })
32     }

三，判断鼠标进入和出去某Dom元素的方式，这种没有利用闭包原理

 1 var gaga = function(wrap) {
 2         var wrap = document.getElementById(wrap);
 3         var hoverDir = function(e) {
 4             var w = wrap.offsetWidth,
 5                 h = wrap.offsetHeight,
 6                 x = (e.clientX - wrap.offsetLeft - (w / 2)) * (w > h ? (h / w) : 1),
 7                 y = (e.clientY - wrap.offsetTop - (h / 2)) * (h > w ? (w / h) : 1),
 8                 // 上(0) 右(1) 下(2) 左(3)  
 9                 direction = Math.round((((Math.atan2(y, x) * (180 / Math.PI)) + 180) / 90) + 3) % 4,
10                 eventType = e.type,
11                 dirName = new Array('上方', '右侧', '下方', '左侧');
12             if (e.type == 'mouseover' || e.type == 'mouseenter') {
13                 wrap.innerHTML = dirName[direction] + '进入';
14             } else {
15                 wrap.innerHTML = dirName[direction] + '离开';
16             }
17         }
18         if (window.addEventListener) {
19             wrap.addEventListener('mouseover', hoverDir, false);
20             wrap.addEventListener('mouseout', hoverDir, false);
21         } else if (window.attachEvent) {
22             wrap.attachEvent('onmouseenter', hoverDir);
23             wrap.attachEvent('onmouseleave', hoverDir);
24         }
25     }

本文结束。