js实现碰撞检测

本文实例为大家分享了js实现碰撞检测的具体代码，供大家参考，具体内容如下

代码：

<!DOCTYPE html><html lang=\"en\"><head><meta charset=\"UTF-8\"><meta name=\"viewport\" content=\"width=device-width, initial-scale=1.0\"><title>Document</title></head><style>div {position: absolute;top: 0px;right: 0px;bottom: 0px;left: 0px;margin: auto;width: 300px;height: 300px;background-color: green;}span {position: absolute;top: 0px;left: 0px;display: block;width: 100px;height: 100px;background-color: rgb(10, 151, 233);}</style><body><div></div><span></span><script>var div = document.getElementsByTagName(\'div\')[0];var span = document.getElementsByTagName(\'span\')[0];span.onmousedown = function(e) {// 事件对象兼容e = window.event || e;// 添加全局捕获if (span.setCapture) {span.setCapture();}// 鼠标按下获取鼠标距离页面左侧和顶部距离var x = e.clientX;var y = e.clientY;// 元素距离页面左侧和顶部距离var elex = span.offsetLeft;var eley = span.offsetTop;// 鼠标距离元素距离 =鼠标距离页面距离 -元素距离页面距离var X = x - elex;var Y = y - eley;document.onmousemove = function(e) {// 鼠标移动 获取鼠标距离页面距离// 事件对象兼容e = window.event || e;var movex = e.clientX;var movey = e.clientY;// 元素的left和top值 =鼠标距离页面距离 -鼠标距离元素距离var leftx = movex - X;var lefty = movey - Y;/*----------------------------------------------------------*/// 碰撞检测// 1.左侧安全距离 =大盒子距离页面左侧距离 -小盒子占位宽var safeleft = div.offsetLeft - span.offsetWidth;// 2.右侧安全距离 大盒子距离页面左侧距离 +大盒子占位宽var saferight = div.offsetLeft + div.offsetWidth;// 3.上侧安全距离 =大盒子距离页面顶部距离 -小盒子占位高var safetop = div.offsetTop - span.offsetHeight;// 4. 下侧安全距离 = 大盒子距离页面顶部距离 + 大盒子占位高var safebottom = div.offsetTop + div.offsetHeight;if (leftx < safeleft || leftx > saferight || lefty < safetop || lefty > safebottom) {div.style.background = \'green\';} else {div.style.background = \'red\';}/*----------------------------------------------------------*/// 边界值// 左if (leftx <= 0) {leftx = 0;}// 上if (lefty <= 0) {lefty = 0;}// 右var rightx = document.documentElement.clientWidth - span.offsetWidth;if (leftx >= rightx)leftx = rightx;// 下var righty = document.documentElement.clientHeight - span.offsetHeight;if (lefty >= righty) {lefty = righty;}span.style.left = leftx + \'px\';span.style.top = lefty + \'px\';}document.onmouseup = function() {document.onmousemove = null;if (span.releaseCapture) {span.releaseCapture();}}// 阻止默认事件return false;}</script></body></html>

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