原生JS完成“一对一、一对多”矩形DIV碰撞检测、碰撞检查，通过计算接触面积(重叠覆盖面积)大小来判断接触对象DOM

//判断两个矩形DIV是否重叠----------------------------------------
function isOver(targetDom, moveDom) {
    if (targetDom === moveDom) return false;
    let tx1 = parseInt(targetDom.style.left);
    let ty1 = parseInt(targetDom.style.top);
    let tx2 = tx1 + parseInt(targetDom.style.width);
    let ty2 = ty1 + parseInt(targetDom.style.height);
    let mx1 = parseInt(moveDom.style.left);
    let my1 = parseInt(moveDom.style.top);
    let mx2 = mx1 + parseInt(moveDom.style.width);
    let my2 = my1 + parseInt(moveDom.style.height);
    let width = Math.min(tx2, mx2) - Math.max(tx1, mx1);
    let height = Math.min(ty2, my2) - Math.max(ty1, my1);
    let stackArea = (width > 0 ? width : 0) * (height > 0 ? height : 0);
    // ----------------------------------------    
    if (stackArea > 0) return true;
    return false;
}

​//判断多个矩形DIV是否重叠，并获取最大的那个----------------------------------------
function isOverManyTarget(targetDom, moveDom) {
    if (targetDom === moveDom) return false;
    let tx1 = parseInt(targetDom.style.left);
    let ty1 = parseInt(targetDom.style.top);
    let tx2 = tx1 + parseInt(targetDom.style.width);
    let ty2 = ty1 + parseInt(targetDom.style.height);
    let mx1 = parseInt(moveDom.style.left);
    let my1 = parseInt(moveDom.style.top);
    let mx2 = mx1 + parseInt(moveDom.style.width);
    let my2 = my1 + parseInt(moveDom.style.height);
    let width = Math.min(tx2, mx2) - Math.max(tx1, mx1);
    let height = Math.min(ty2, my2) - Math.max(ty1, my1);
    let stackArea = (width > 0 ? width : 0) * (height > 0 ? height : 0);
 
    // ----------------------------------------
 
    //计算面积
 
    let measure = parseInt(targetDom.style.width) * parseInt(targetDom.style.height);
    let measureHalf = measure / 2;
    if (stackArea > measureHalf && stackArea <= measure) return targetDom;
 
    return null;
}