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

    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);
        }
    }

本文结束。