javascript - 返回 false 不会阻止表单提交

Question

我需要使用 JavaScript 验证表单，并且需要同时显示所有消息。例如，如果缺少名字和姓氏，则会出现两条消息。我已经使用下面的代码解决了这个问题，但表单仍然被返回到服务器。 P 租赁见下文:

function validateForm() {
    var flag = true;
    var x = document.forms["myForm"]["firstname_4"].value;
    if (x == null || x == "") {
        document.getElementById("fNameMessage").innerHTML = "First name is  required";
        flag = false;
    } else {
        document.getElementById("fNameMessage").innerHTML = "";
    }

    var x = document.forms["myForm"]["surname_5"].value;
    if (x == null || x == "") {
        document.getElementById("sNameMessage").innerHTML = "Surename is required";
        flag = false;
    } else {
        document.getElementById("sNameMessage").innerHTML = "";
    }
    var y = document.forms["myForm"]["selectid"];
    if (y.options[y.selectedIndex].value == "Title") {
        document.getElementById("titleMessage").innerHTML = "You need to select a title";
        flag = false;
    } else {
        document.getElementById("titleMessage").innerHTML = "";
    }

    return flag;
}

我的表格和事件:

<form action=""method="post" accept-charset="UTF-8" name="myForm" onsubmit="return validateForm();">

我的按钮:

<input type="submit" class="button" name="submit" id="submit" value="Submit">

Answer 1

您的代码:

var y = document.forms["myForm"]["selectid"];
if (y.options[y.selectedIndex].value == "Title") 

...触发异常但您没有捕获它:

Uncaught TypeError: Cannot read property 'options' of undefined

因此 JavaScript 代码停止运行。