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javascript - onsubmit method doesn't stop submit

My onsubmit is not working. My idea was to put some mandatory fields and, in order to achieve that, I was using the onsubmit method inside a form in HTML that called a JavaScript function.

The idea was if all the mandatory fields were filled, the javascript function would return true and it would move on to page /control/Cadastro.php. Otherwise, if any mandatory field was empty, it would return false and it wouldn't move to page /control/Cadastro.php, staying in the current page until true.

Unfortunately, the function does return false if all the mandatory fields are not filled, as expected, but it still moves to page /control/Cadastro.php, even if it shouldn't.

I'm going to cut off some code to make my point of view perceptible.

<!DOCTYPE html>
<html>
    <head>
        <script>
            function ValidateRequiredFields()
            {
                var message = new String('
Campos obrigatórios:
');
                var flag=new Boolean(1);
                var x=document.forms["theForm"]["nr_processoCA"].value;
                if (x==null || x==""){
                    message += '
No do processo
'; 
                    flag = new Boolean(0);
                } 
                if (flag == false){
                    alert(message);
                }
                return flag;    
            }
        </script>
    </head>
    <body>
        <form name="theForm" onsubmit="return ValidateRequiredFields()" method="post" action="../control/Cadastro.php"> 
            No do Processo: <br>
            <input type="text" name="nr_processoCA" class="input-xlarge">
            <br>
            <div class="row-fluid" style="text-align:center;">
                <input type="submit" class="btn btn-primary btn-large" value="Gravar">
            </div>   
         </form>
    </body>
</html>
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1 Answer

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by (71.8m points)

You should use preventDefault inside your onsubmit function. I modified your code:

function ValidateRequiredFields()
{
    var message = new String('
Campos obrigatórios:
');
    var flag=new Boolean(1);


    var x=document.forms["theForm"]["nr_processoCA"].value;
    if (x==null || x==""){
        message += '
No do processo
'; 
        flag = new Boolean(0);
    }

    if (flag == false){
        if(event.preventDefault){
            event.preventDefault();
        }else{
            event.returnValue = false; // for IE as dont support preventDefault;
        }
        alert(message);
    }

    return flag;
}

DEMO


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