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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