Q:

validar  com Javascript

Estou tentando validar um <form> com JavaScript, mas o código que criei não está fazendo nada. me parece correto.
Código HTML
<form name="ContactForm" action="addDataAdmin.php" method="POST" enctype="multipart/form-data" autocomplete="off" onsubmit="return ValidateContactForm();">
  <p>ISBN</p> <input type="text" name="ISBN">
  <p>Author's Name</p> <input type="text" name="Authorsname">
  <p>Title</p> <input type="text" name="Title">
  <p>Edition</p> <input type="text" name="edition">
  <p>Year</p> <input type="text" name="year">

  <p>Category</p>
  <select name="category" size="1">
      <option value="computing">Computing</option>
      <option value="Romance">Romance</option>
      <option value="Fiction">Fiction</option>
      <option value="Non-Fiction">Non-Fiction</option>
  </select>
  <br />

  <p>Publisher</p> <input type="text" name="publisher">
  <p>Quantity-in-stock</p> <input type="text" name="quantityinstock">
  <p>Price</p> <input type="text" name="price">
  <input type="file" name="fileToUpload" id="fileToUpload">
  <input type="submit" value="Upload Image" name="submit" formaction="/upload.php">
  <input type="submit" value="Send" name="send">
  <input type="reset" value="Clear">
</form>

Script
function ValidateContactForm()
{
    var ISBN = document.ContactForm.ISBN;
    var Authorsname = document.ContactForm.Authorsname;
    var Title = document.ContactForm.Title; 
    var edition = document.ContactForm.edition;
    var year= document.ContactForm.year;
    var category = document.ContactForm.category;
    var publisher = document.ContactForm.publisher;
    var quantityinstock= document.ContactForm.quantityinstock;
    var price = document.ContactForm.price;
}

if (ISBN.value == "")
{
    window.alert("Please enter ISBN.");
    ISBN.focus();
    return false;
}

A:

A chave que fecha a função ValidateContactForm tá no lugar errado.
Este if (ISBN.value == "") tá perdido no código, ele deveria estar dentro da função que faz a validação.
Veja funcionando (tirei boa parte do código pra facilitar a leitura).

function ValidateContactForm()
{
    var ISBN = document.ContactForm.ISBN;
    
    if (ISBN.value == "")
    {
        window.alert("Please enter ISBN.");
        ISBN.focus();
        return false;
    }
}
<form name="ContactForm" method="GET" onsubmit="return ValidateContactForm();">
  <p>ISBN</p> <input type="text" name="ISBN">
  
  <input type="submit" value="Send" name="send">
</form>

