javascript动画之磁性吸附效果篇

function limitedRange(obj,fn){  var L0 = 0;  var R0 = document.documentElement.clientWidth;  var T0 = 0;  var B0 = document.documentElement.clientHeight;  var L = obj.offsetLeft;  var R = obj.offsetLeft + obj.offsetWidth;  var T = obj.offsetTop;  var B = obj.offsetTop + obj.offsetHeight;  if(L >= L0 && R <= R0 && T >= T0 && B <= B0){    fn(obj);  }}

<div id="test" style="height: 100px;width: 100px;background:pink;position:absolute;top:0;left:0;">测试文字</div><script>function drag(obj){  obj.onmousedown = function(e){    e = e || event;    //获取元素距离定位父级的x轴及y轴距离    var x0 = this.offsetLeft;    var y0 = this.offsetTop;    //获取此时鼠标距离视口左上角的x轴及y轴距离    var x1 = e.clientX;    var y1 = e.clientY;    //鼠标按下时，获得此时的页面区域    var L0 = 0;    var R0 = document.documentElement.clientWidth;    var T0 = 0;    var B0 = document.documentElement.clientHeight;    //鼠标按下时，获得此时的元素宽高    var EH = obj.offsetHeight;    var EW = obj.offsetWidth;    document.onmousemove = function(e){      e = e || event;      //获取此时鼠标距离视口左上角的x轴及y轴距离      x2 = e.clientX;      y2 = e.clientY;        //计算此时元素应该距离视口左上角的x轴及y轴距离      var X = x0 + (x2 - x1);      var Y = y0 + (y2 - y1);      /******范围限定*******/      //获取鼠标移动时元素四边的瞬时值      var L = X;      var R = X + EW;      var T = Y;      var B = Y + EH;      //在将X和Y赋值给left和top之前，进行范围限定      //只有在范围内时，才进行相应的移动      //如果脱离左侧范围，则left置L0      if(L < L0){X = L0;}      //如果脱离右侧范围，则left置为R0      if(R > R0){X = R0 - EW;}      //如果脱离上侧范围，则top置T0      if(T < T0){Y = T0;}      //如果脱离下侧范围，则top置为B0      if(B > B0){Y = B0 - EH;}      obj.style.left = X + 'px';      obj.style.top = Y + 'px';    }    document.onmouseup = function(e){      //当鼠标抬起时，拖拽结束，则将onmousemove赋值为null即可      document.onmousemove = null;      //释放全局捕获      if(obj.releaseCapture){        obj.releaseCapture();      }    }    //阻止默认行为    return false;    //IE8-浏览器阻止默认行为    if(obj.setCapture){      obj.setCapture();    }  }  }drag(test);</script>

<div id="test" style="height: 100px;width: 100px;background:pink;position:absolute;top:0;left:0;">测试文字</div><script>function drag(obj){  obj.onmousedown = function(e){    e = e || event;    //获取元素距离定位父级的x轴及y轴距离    var x0 = this.offsetLeft;    var y0 = this.offsetTop;    //获取此时鼠标距离视口左上角的x轴及y轴距离    var x1 = e.clientX;    var y1 = e.clientY;    //鼠标按下时，获得此时的页面区域    var L0 = 0;    var R0 = document.documentElement.clientWidth;    var T0 = 0;    var B0 = document.documentElement.clientHeight;    //鼠标按下时，获得此时的元素宽高    var EH = obj.offsetHeight;    var EW = obj.offsetWidth;    document.onmousemove = function(e){      e = e || event;      //获取此时鼠标距离视口左上角的x轴及y轴距离      x2 = e.clientX;      y2 = e.clientY;        //计算此时元素应该距离视口左上角的x轴及y轴距离      var X = x0 + (x2 - x1);      var Y = y0 + (y2 - y1);      /******磁性吸附*******/      //获取鼠标移动时元素四边的瞬时值      var L = X;      var R = X + EW;      var T = Y;      var B = Y + EH;      //在将X和Y赋值给left和top之前，进行范围限定      //只有在范围内时，才进行相应的移动      //如果到达左侧的吸附范围，则left置L0      if(L - L0 < 50){X = L0;}      //如果到达右侧的吸附范围，则left置为R0      if(R0 - R < 50){X = R0 - EW;}      //如果到达上侧的吸附范围，则top置T0      if(T - T0 < 50){Y = T0;}      //如果到达右侧的吸附范围，则top置为B0      if(B0 - B < 50){Y = B0 - EH;}      obj.style.left = X + 'px';      obj.style.top = Y + 'px';    }    document.onmouseup = function(e){      //当鼠标抬起时，拖拽结束，则将onmousemove赋值为null即可      document.onmousemove = null;      //释放全局捕获      if(obj.releaseCapture){        obj.releaseCapture();      }    }    //阻止默认行为    return false;    //IE8-浏览器阻止默认行为    if(obj.setCapture){      obj.setCapture();    }  }  }drag(test);</script>