PHP JS createElement创建DIV getElementById 获取错误！！！

解决方案 »

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你应该把所有的代码贴出来，包括HTML，否则人没办法分析。
trim(document.getElementById('login_name').value)=="")
js没有trim这个函数吧
找到原因了，是因为你缺少函数trim（）。
帮你写了个：
function trim(str){
return str.replace(/^\s+/gi, '').replace(/\s+$/gi, '');
}<script type="text/javascript">
function login(){
    var w = 300;
    var h = 155;
    var title = '登陆';
    var titleheight = "22pxpx"; // 提示窗口标题高度
    var bordercolor = "#8B0000"; // 提示窗口的边框颜色
    var titlecolor = "#FFFFFF"; // 提示窗口的标题颜色
    var titlebgcolor = "#8B0000"; // 提示窗口的标题背景色
    var bgcolor = "#FFFFFF"; // 提示内容的背景色
    var msg;

    //var iWidth = document.documentElement.clientWidth;
    //var iHeight = document.documentElement.clientHeight;
    var iWidth = document.body.clientWidth;
    var iHeight = document.body.clientHeight;
    var bgObj = document.createElement("div");     //背景变暗宽高document.body.scrollLeft
    bgObj.style.cssText = "position:absolute;left:0px;top:0px;width:"+window.screen.width+"px;height:"+Math.max(document.body.scrollHeight)+"px;filter:Alpha(Opacity=30);opacity:0.3;background-color:#000000;z-index:101;";
    document.body.appendChild(bgObj);
    //DIV显示位置
    var msgObj=document.createElement("div");
    //msgObj.style.cssText = "position:absolute;font:11px '宋体';top:"+(iHeight-h)/2+"px;left:"+(iWidth-w)/2+"px;width:"+w+"px;height:"+h+"px;border:1px solid "+bordercolor+";background-color:"+bgcolor+";padding:1px;line-height:22px;z-index:102;";
    msgObj.style.cssText = "position:absolute;font:11px '宋体';top:"+(iHeight-h)/2+"px;left:"+(iWidth-w)/2+"px;width:"+w+"px;height:"+h+"px !important;height:170px;border:1px solid "+bordercolor+";background-color:"+bgcolor+";padding:1px;line-height:22px;z-index:102;";
    document.body.appendChild(msgObj);     var table = document.createElement("table");
    msgObj.appendChild(table);
    table.style.cssText = "margin:0px;border:0px;padding:0px;";
    table.cellSpacing = 0;
    var tr = table.insertRow(-1);
    var titleBar = tr.insertCell(-1);
    titleBar.style.cssText = "width:100%;height:"+titleheight+"px;text-align:left;padding:3px;margin:0px;font:bold 13px '宋体';color:"+titlecolor+";border:1px solid " + bordercolor + ";cursor:move;background-color:" + titlebgcolor;
    titleBar.style.paddingLeft = "10px";
    titleBar.innerHTML = title;
    var moveX = 0;
    var moveY = 0;
    var moveTop = 0;
    var moveLeft = 0;
    var moveable = false;
    var docMouseMoveEvent = document.onmousemove;
    var docMouseUpEvent = document.onmouseup;
    titleBar.onmousedown = function() {
        var evt = getEvent();
        moveable = true;
        moveX = evt.clientX;
        moveY = evt.clientY;
        moveTop = parseInt(msgObj.style.top);
        moveLeft = parseInt(msgObj.style.left);

        document.onmousemove = function() {
            if (moveable) {
                var evt = getEvent();
                var x = moveLeft + evt.clientX - moveX;
                var y = moveTop + evt.clientY - moveY;
                if ( x > 0 &&( x + w < iWidth) && y > 0 && (y + h < iHeight) ) {
                    msgObj.style.left = x + "px";
                    msgObj.style.top = y + "px";
                }
            }
        };
        document.onmouseup = function () {
            if (moveable) {
                document.onmousemove = docMouseMoveEvent;
                document.onmouseup = docMouseUpEvent;
                moveable = false;
                moveX = 0;
                moveY = 0;
                moveTop = 0;
                moveLeft = 0;
            }
        };
    }

    var closeBtn = tr.insertCell(-1);
    closeBtn.style.cssText = "cursor:pointer; padding:2px;background-color:" + titlebgcolor;
    closeBtn.innerHTML = "<div style='font-size:12pt; color:"+titlecolor+";text-align:right;'>×</div>";
    closeBtn.onclick = function (){
        document.body.removeChild(bgObj);
        document.body.removeChild(msgObj);
    }
    var msgBox = table.insertRow(-1).insertCell(-1);
    msgBox.style.cssText = "font:10pt '宋体';";
    msgBox.colSpan = 2;
    msg = "<div style='margin:5px 0 0 0;overflow:hidden;width:"+w+"px!important;width:275px'>"+
                     "<div style='width:"+w+"px;overflow:hidden;'>"+
                             "<div style='float:left;margin:10px 0 0 20px;line-height:20px;width:55px;'>用户名：</div>"+
                             "<div style='float: left;margin:10px 0 0 0;'>"+
                                    "<input type='text' name='login_name' id='login_name' style='border:1px solid #999;width:150px;'/>"+
                                    "<span ><a href='#'>立即注册</a></span>"+
                             "</div>"+
                     "</div>"+
                     "<div style='width:"+w+"px;overflow:hidden;'>"+
                             "<div style='float:left;margin:10px 0 0 20px;line-height:20px;width:55px;'>密码：</div>"+
                             "<div style='float: left;margin:10px 0 0 0;'>"+
                                    "<input type='password' name='login_pass' onKeyDown='if(event.keyCode==32) return false'"+
                                             "id='password1' maxlength='16' onKeyPress='if (event.keyCode==32) {event.returnvalue=false;return false;}' style='border:1px solid #999;width:150px;'/>"+
                                    "<span ><a href='#'>忘记密码</a></span>"+
                             "</div>"+
                     "</div>"+
                     "<div style='width:"+w+"px;overflow:hidden;'>"+
                             "<div style='float:left;margin:10px 0 0 20px;line-height:20px;width:55px;'>验证码：</div>"+
                             "<div style='float: left;margin:10px 0 0 0;'>"+
                                    "<input type='text' name='checkcode' style='border:1px solid #999;width:60px;'/>"+
                             "</div>"+
                             "<div style='float: left;margin:10px 0 0 0;'>"+
                                    "<input type='text' name='code' style='border:1px solid #999;width:90px;'/>"+
                                    "<span ><a href='#'>看不清楚</a></span>"+
                             "</div>"+
                     "</div>"+
                     "<div style='width:"+w+"px;overflow:hidden;'>"+
                              "<div style='float:left;margin:10px 0 0 170px !important;margin:10px 0 0 90px;'>"+
                                      "<input type='button' name='submit' value='确定' onClick='return createuser_login();' />"+
                              "</div>"+
                              "<div style='float:left;margin:10px 0 0 5px;'><input type='button' name='exit' value='取消'/></div>"+
                     "</div>"+
            "</div>";
    msgBox.innerHTML = msg;
        // 获得事件Event对象，用于兼容IE和FireFox
    function getEvent() {
        return window.event || arguments.callee.caller.arguments[0];

    }
} function trim(str){
return str.replace(/^\s+/gi, '').replace(/\s+$/gi, '');
}
function createuser_login(){
    var b=true;
    if(trim(document.getElementById('login_name').value)==""){
        alert("对不起,请输入您的用户名！");
        document.getElementById('login_name').select();
        b=false;
        return b;
    }
    if(document.getElementById('login_pass').value.indexOf(" ")>-1){
        alert("登录密码不能包含空格！");
        document.getElementById('login_pass').select();
        b=false;
        return b;
    }
    if(trim(document.getElementById('login_pass').value)==""){
        alert("请输入您的登录密码！");
        document.getElementById('login_pass').select();
        b=false;
        return b;
    }
    return b;
}</script><body>
<button onclick="login()">Show</button>
</body>