[Javascript]實現html表單欄位空白檢查

html form(檢查觸發在onClick上)

<form action="login/doLogin" method="post" name="f_login">
<?php echo csrf_field(); ?>
<input type="text" name="login_email" id="eamil" class="form-control" placeholder="帳號或信箱"  /></br>
<input type="password" name="login_pwd" id="pwd" class="form-control" placeholder="密碼"  /></br>

<input type=button VALUE="登入" class="btn btn-lg btn-primary btn-block" onClick="validateForm(this.form)">
<br>
</form>

javascript(放置在head)

<script>
function validateForm(form){
  if(form.login_email.value==""
    || form.login_pwd.value==""){
    alert("帳號或是密碼欄不得為空");
    return -1;
  }
 form.submit();
 return 0;
}
</script>