鼠标拖拉实现元素批量选择效果

核心JS结构

(function() { 
  document.onmousedown = function() { 
    var selList = []; 
    var fileNodes = document.getElementsByTagName("div"); 
    for ( var i = 0; i < fileNodes.length; i++) { 
      if (fileNodes[i].className.indexOf("fileDiv") != -1) { 
        fileNodes[i].className = "fileDiv"; 
        selList.push(fileNodes[i]); 
      } 
    } 
    var isSelect = true; 
    var evt = window.event || arguments[0]; 
    var startX = (evt.x || evt.clientX); 
    var startY = (evt.y || evt.clientY); 
    var selDiv = document.createElement("div"); 
    selDiv.style.cssText = "position:absolute;width:0px;height:0px;font-size:0px;margin:0px;padding:0px;border:1px dashed #0099FF;background-color:#C3D5ED;z-index:1000;filter:alpha(opacity:60);opacity:0.6;display:none;"; 
    selDiv.id = "selectDiv"; 
    document.body.appendChild(selDiv); 
    selDiv.style.left = startX + "px"; 
    selDiv.style.top = startY + "px"; 
    var _x = null; 
    var _y = null; 
    clearEventBubble(evt); 
    document.onmousemove = function() { 
      evt = window.event || arguments[0]; 
      if (isSelect) { 
        if (selDiv.style.display == "none") { 
          selDiv.style.display = ""; 
        } 
        _x = (evt.x || evt.clientX); 
        _y = (evt.y || evt.clientY); 
        selDiv.style.left = Math.min(_x, startX) + "px"; 
        selDiv.style.top = Math.min(_y, startY) + "px"; 
        selDiv.style.width = Math.abs(_x - startX) + "px"; 
        selDiv.style.height = Math.abs(_y - startY) + "px"; 
        // ---------------- 关键算法 ---------------------  
        var _l = selDiv.offsetLeft, _t = selDiv.offsetTop; 
        var _w = selDiv.offsetWidth, _h = selDiv.offsetHeight; 
        for ( var i = 0; i < selList.length; i++) { 
          var sl = selList[i].offsetWidth + selList[i].offsetLeft; 
          var st = selList[i].offsetHeight + selList[i].offsetTop; 
          if (sl > _l && st > _t && selList[i].offsetLeft < _l + _w && selList[i].offsetTop < _t + _h) { 
            if (selList[i].className.indexOf("seled") == -1) { 
              selList[i].className = selList[i].className + " seled"; 
            } 
          } else { 
            if (selList[i].className.indexOf("seled") != -1) { 
              selList[i].className = "fileDiv"; 
            } 
          } 
        } 
      } 
      clearEventBubble(evt); 
    } 
    document.onmouseup = function() { 
      isSelect = false; 
      if (selDiv) { 
        document.body.removeChild(selDiv); 
        showSelDiv(selList); 
      } 
      selList = null, _x = null, _y = null, selDiv = null, startX = null, startY = null, evt = null; 
    } 
  } 
})();
 
function clearEventBubble(evt) { 
  if (evt.stopPropagation) 
    evt.stopPropagation(); 
  else 
    evt.cancelBubble = true; 
  if (evt.preventDefault) 
    evt.preventDefault(); 
  else 
    evt.returnValue = false; 
} 
function showSelDiv(arr) { 
  var count = 0; 
  var selInfo = ""; 
  for ( var i = 0; i < arr.length; i++) { 
    if (arr[i].className.indexOf("seled") != -1) { 
      count++; 
      selInfo += arr[i].innerHTML + "\n"; 
    } 
  } 
  alert("共选择 " + count + " 个文件，分别是：\n" + selInfo); 
}