Using jQuery to prevent form submission when input

问题:

The solution should be pretty straightforward. I'm trying to prevent the form from submitting properly when no value is found within the input boxes. Here's my JSFiddle: http://jsfiddle.net/nArYa/7/

//Markup

<form action="" method="post" name="form" id="form">
<input type="text" placeholder="Your email*" name="email" id="email">
<input type="text" placeholder="Your name*" autocomplete=off name="name" id="user_name"
<button type="submit" id="signup" value="Sign me up!">Sign Up</button>
</form>

//jQuery

if ($.trim($("#email, #user_name").val()) === "") {
    $('#form').submit(function(e) {
        e.preventDefault();
        alert('you did not fill out one of the fields');
    })
} 

As you can see in the JSFiddle, the problem is that when I type something into both fields, the alert box STILL pops up. I'm having a hard time figuring out why. Is there something wrong within my if($.trim($"#email, #user_name").val()) === "") ?

回答1:

Two things, #1 the check for empty fields should happen on every attempt of submit, #2 you need to check each field individually

$('#form').submit(function() {
    if ($.trim($("#email").val()) === "" || $.trim($("#user_name").val()) === "") {
        alert('you did not fill out one of the fields');
        return false;
    }
});

Updated fiddle

回答2:

Your check occurs on page load. You need to check the field when the form is submitted.

$('#form').submit(function(e) {
    if ($.trim($("#email, #user_name").val()) === "") {
        e.preventDefault();
        alert('you did not fill out one of the fields');
    }
});

回答3:

HTML5: use required in input tag

• A boolean attribute.

• Input field must be filled out before submitting the form.

• Works with text, search, url, tel, email, password, date pickers, number, checkbox, radio, and file.

  <input required type='text'...>
  

w3schools hint

回答4:

I guess that this will help:

$('#form').submit(function(e) {
    e.preventDefault();
    $("#email, #user_name").each(function(){
        if($.trim(this.value) == ""){
            alert('you did not fill out one of the fields');
        } else {
            // Submit 
        }
    })
})

回答5:

Put your if statement inside the callback:

$('#form').submit(function(e) {
    if ($.trim($("#email").val()) === "" || $.trim($("#user_name").val())) {
        e.preventDefault();
        alert('you did not fill out one of the fields');
        //You can return false here as well
    }
});