JS实现利用闭包判断Dom元素和滚动条的方向示例

本文实例讲述了JS实现利用闭包判断Dom元素和滚动条的方向。分享给大家供大家参考，具体如下：

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

function scroll(fn) {
    //利用闭包判断滚动条滚动的方向
    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、判断鼠标的移动方向

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);
      // 初始化坐标
      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

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', '右侧', '下方', '左侧');
      if (e.type == 'mouseover' || e.type == 'mouseenter') {
        wrap.innerHTML = dirName[direction] + '进入';
      } else {
        wrap.innerHTML = dirName[direction] + '离开';
      }
    }
    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);
    }
}

希望本文所述对大家JavaScript程序设计有所帮助。