Javascript 对象在 IE 中为 null 或不是对象

Question

我有一个由javascript添加了复选框的表单，提交表单时它会检查该复选框是否已被选中。这在 Firefox 或 Chrome 中工作正常，但在 IE7 或 8 中会导致错误 document.myform.mycheckbox.checked 为 null 或不是对象。

var checkbox = document.createElement("input");
checkbox.type = "checkbox";
checkbox.name = "mycheckbox";
checkbox.value= 291;
var div = document.getElementById("addcb");
div.appendChild(checkbox);
checkbox.checked = false;

在表单标签中，我有 onSubmit="return CheckForm();"，它在 Firefox 或 Chrome 中工作正常，但在 IE7 或 8 中，它提交表单而不检查表单或其他表单对象。

if (document.myform.mycheckbox.checked == false){
    errorMsg += "\n\tAgree \t- Please Click I Agree Checkbox";
}

//If there is aproblem with the form then display an error
if ((errorMsg != "") || (errorMsgLong != "")){
    msg = "_______________________________________________________________\n\n";
    msg += "The form has not been submitted because there are problem(s) with the form.\n";
    msg += "Please correct the problem(s) and re-submit the form.\n";
    msg += "_______________________________________________________________\n\n";
    msg += "The following field(s) need to be corrected: -\n";

    errorMsg += alert(msg + errorMsg + "\n" + errorMsgLong);
    return false;
}

return true;

我使用开发者工具创建了一个报告错误的 Brakpoint:

document.myform.mycheckbox.checked is null or not an object

Answer 1

创建它时，也给它一个 ID

checkbox.id = "mycheckbox";

然后找到它执行

if (document.getElementById("mycheckbox").checked == false)