javascript - 在验证后将焦点设置到文本框表单元素

Question

我在表单上有多个字段执行验证，如果验证失败，我希望关注焦点这些字段。验证工作正常，即 rtnStr，但 focus() 不会落在任何文本框字段上，即 vCtrl。它保留在“提交”按钮上。

<script language="javascript">

function ValidateForm() {
    var rtnStr = "";
    var vCtrl = "";

    //Contact Details //
    if (document.contactform.txtforename.value == "") {
        rtnStr = rtnStr + " - Please enter your Forename.\n"
        if (vCtrl == "") {
            vCtrl = "txtforename";
        }
    }

    if (document.contactform.txtSurname.value == "") {
        rtnStr = rtnStr + " - Please enter your Surname.\n"
        if (vCtrl == "") {
            vCtrl = "txtSurname";
        }
    }

    if (rtnStr != "") {
        alert(rtnStr)
        window.setTimeout(function () {
            document.getElementById(vCtrl).focus();
        }, 0);
        return false;
    }
    else {
        return true;
    }
}               
</script>

Answer 1

问题在于 vCtrl 是一个字符串，它是表单的名称，而不是 document.getElementById(vCtrl).focus() 正在查找的id 。解决这个问题的方法是让 vCtrl 存储 DOM 元素而不是文本字符串。

<script  language="javascript">
    function ValidateForm() {
    var rtnStr = "";
    var vCtrl = "";
    //Contact Details //
    if (document.contactform.txtforename.value == "") {
        rtnStr = rtnStr + " - Please enter your Forename.\n"
        if (vCtrl == "") {
            vCtrl = document.contactform.txtforename;
        }
    }

    if (document.contactform.txtSurname.value == "") {
        rtnStr = rtnStr + " - Please enter your Surname.\n"
        if (vCtrl == "") {
            vCtrl = document.contactform.txtSurname;
        }
    }

    if (rtnStr != "") {
        alert(rtnStr)

        vCtrl.focus();

        return false;
    }
    else {
        return true;
    }
}
</script>

jsfiddle