javascript 的单选按钮验证表单

Question

尝试验证单选按钮（以及其他验证）；但是，每当验证单选按钮时，一切都会重置，甚至不会说“表单已提交”或验证表单的下一部分。

function submit() {
  alert("The form was submitted");
}


function validate() {
  if (document.myForm.user.value.length < 6) {
    alert("Please enter a username that is at least 6 characters long");
    document.myForm.user.focus();
    return false;
  }

  if (document.myForm.pass.value.length < 6) {
    alert("Please enter a password that is at least 6 characters long.");
    document.myForm.pass.focus();
    return false;
  }

  if (document.myForm.pass.value != document.myForm.pass1.value) {
    alert("Your passwords do not match! Please re-enter your password!");
    document.myForm.pass1.focus();
    return false;
  }

  if (document.myForm.first.value == "") {
    alert("Please provide your First name!");
    document.myForm.first.focus();
    return false;
  }

  if (document.myForm.last.value == "") {
    alert("Please provide your Last name!");
    document.myForm.last.focus();
    return false;
  }

  if (document.myForm.address.value == "") {
    alert("Please provide your Address!");
    document.myForm.address.focus();
    return false;
  }

  if (document.myForm.city.value == "") {
    alert("Please provide your City!");
    document.myForm.city.focus();
    return false;
  }

  if (document.myForm.state.value == "") {
    alert("Please provide your State!");
    document.myForm.state.focus();
    return false;
  }

  if (document.myForm.zip.value == "" ||
    document.myForm.zip.value.length != 5) {
    alert("Please provide a Zip code in the format #####.");
    document.myForm.zip.focus();
    return false;
  }
  var zip = /^[0-9a]+$/;
  if (!document.myForm.zip.value.match(zip)) {
    alert("Please only enter numeric characters for the Zip code");
    document.myForm.zip.focus();
    return false;
  }

  if (document.myForm.creditcard[0].checked = true) {
    return true;
  } else if (document.myForm.creditcard[1].checked == true) {
    return true;
  } else if (document.myform.creditcard[2].checked == true) {
    return true;
  } else {
    alert("Please choose your credit card type!");
    return false;
  }

  if (document.myForm.creditno.value == "" ||
    document.myForm.creditno.value.length < 13) {
    alert("Please provide a valid credit card number!");
    document.myForm.creditno.focus();
    return false;
  }

  if (!document.myForm.creditno.value.match(zip)) {
    alert("Please provide a valid credit card number!");
    document.myForm.creditno.focus();
    return false;
  }

  alert("The form was submitted");
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<p>
  <form action="" name="myForm" onsubmit="return (validate())" ;>
    Username:
    <input name="user" type="text" size="25">
    <br>Password:
    <input name="pass" type="password" size="20">
    <br>Confirm Password:
    <input name="pass1" type="password" size="20">
    <br>First Name:
    <input name="first" type="text" size="30">
    <br>Last Name:
    <input name="last" type="text" size="30">
    <br>
    <br>Address:
    <input name="address" type="text" size="50">
    <br>City:
    <input name="city" type="text" size="35">
    <br>State:
    <input name="state" type="text" size="25">
    <br>Zip Code:
    <input name="zip" type="text" size="5">
    <br>
    <br>**Credit Card:
    <br>
    <input name="creditcard" type="radio">Visa
    <br>
    <input name="creditcard" type="radio">Mastercard
    <br>
    <input name="creditcard" type="radio">American Express
    <br>
    <br>** Credit Card #.
    <input name="creditno" type="password" size="25">
    <br>
    <br>We welcome your comments and feedback:
    <br>
    <textarea maxlength="100"></textarea>
    <br>
    <input type=submit value="Submit Query">
    <input type=reset>

  </form>

</p>

Answer 1

替换这个

if (document.myForm.creditcard[0].checked = true) {
    return true;
  } else if (document.myForm.creditcard[1].checked == true) {
    return true;
  } else if (document.myform.creditcard[2].checked == true) {
    return true;
  } else {
    alert("Please choose your credit card type!");
    return false;
  }

有了这个

chosen = "";
len = document.myForm.creditcard.length;

for (i = 0; i <len; i++) {
    if (document.myForm.creditcard[i].checked) {
        chosen = document.myForm.creditcard[i].value
    }
}

if (chosen == "") {
    alert("Please choose your credit card type!");
    return false;
}