本文實(shí)例講述了JS實(shí)現(xiàn)利用閉包判斷Dom元素和滾動(dòng)條的方向。分享給大家供大家參考，具體如下：

一、判斷滾動(dòng)條的方向，利用閉包首先保存滾動(dòng)條的位置，然后當(dāng)滾動(dòng)時(shí)候不斷更新滾動(dòng)初始值，然后通過差指判斷方向

function scroll(fn) {    //利用閉包判斷滾動(dòng)條滾動(dòng)的方向    var beforeScrollTop = document.body.scrollTop,      fn = fn || function() {};    window.addEventListener("scroll", function() {      var afterScrollTop = document.body.scrollTop,        delta = afterScrollTop - beforeScrollTop;      if (delta === 0) return false;      fn(delta > 0 ? "down" : "up");      beforeScrollTop = afterScrollTop;    }, false);}scroll(function(direction) { console.log(direction) });

二、判斷鼠標(biāo)的移動(dòng)方向

function direction() {    var lastX = null,      lastY = null;    window.addEventListener("mousemove", function(event) {      var curX = event.clientX,        curY = event.clientY,        direction = '';      // console.info(event);      // console.info(event.clientX);      // console.info(event.clientY);      // 初始化坐標(biāo)      if (lastX == null || lastY == null) {        lastX = curX;        lastY = curY;        return;      }      if (curX > lastX) {        direction += 'X右,';      } else if (curX < lastX) {        direction += 'X左,';      }      if (curY > lastY) {        direction += 'Y下';      } else if (curY < lastY) {        direction += 'Y上';      }      lastX = curX;      lastY = curY;      //console.info(direction);      document.getElementById("test").innerText = direction;    })}

三、判斷鼠標(biāo)進(jìn)入和出去某Dom元素的方式，這種沒有利用閉包原理

var gaga = function(wrap) {    var wrap = document.getElementById(wrap);    var hoverDir = function(e) {      var w = wrap.offsetWidth,        h = wrap.offsetHeight,        x = (e.clientX - wrap.offsetLeft - (w / 2)) * (w > h ? (h / w) : 1),        y = (e.clientY - wrap.offsetTop - (h / 2)) * (h > w ? (w / h) : 1),        // 上(0) 右(1) 下(2) 左(3)         direction = Math.round((((Math.atan2(y, x) * (180 / Math.PI)) + 180) / 90) + 3) % 4,        eventType = e.type,        dirName = new Array('上方', '右側(cè)', '下方', '左側(cè)');      if (e.type == 'mouseover' || e.type == 'mouseenter') {        wrap.innerHTML = dirName[direction] + '進(jìn)入';      } else {        wrap.innerHTML = dirName[direction] + '離開';      }    }    if (window.addEventListener) {      wrap.addEventListener('mouseover', hoverDir, false);      wrap.addEventListener('mouseout', hoverDir, false);    } else if (window.attachEvent) {      wrap.attachEvent('onmouseenter', hoverDir);      wrap.attachEvent('onmouseleave', hoverDir);    }}

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