function f_check_NumOrLett(form){    //Only letters and numbers allowed  

        var text = form.bucketname.value;
        alert(text);

        var filter = /^[A-Za-z0-9]+$/;
        if (filter.test(text)) {
            form.submit(); 
        } else {
            form.bucketname.select();
            alert("Only Allow letters and numbers!");
        }
    }  

When I use this function, alert(text) can work, but it cannot neither submit the form or alert "Only allow letters and numbers" message. It seems it didn't excute IF condition.

    function f_check_NumOrLett(form){    //Only letters and numbers allowed  

        var text = form.bucketname.value;
        alert(text);

        var filter = /^[A-Za-z0-9]+$/;
        if (filter.test(text)) {
            form.submit(); 
        } else {
            form.bucketname.select();
            alert("Only Allow letters and numbers!");
        }
    }  

When I use this function, alert(text) can work, but it cannot neither submit the form or alert "Only allow letters and numbers" message. It seems it didn't excute IF condition.

• javascript

• I don't get what you mean by "it cannot access into if condition". Can you make it clearer ? – Denys Séguret Commented Dec 10, 2012 at 16:26
• what task are you trying to acplish? what have you done so far to try and solve the task? why didn't your approach work? – jbabey Commented Dec 10, 2012 at 16:27
• 2 I don't see how it could fail between the first alert and the if blocks. Can you build a fiddle ? Are you sure you don't have intermediate code ? – Denys Séguret Commented Dec 10, 2012 at 16:35

1 Answer 1

If you're cool with supporting new browsers and no legacy, you can use the new pattern attribute which is available on input elements (which I think you're using here)

Example:

<input type="text" pattern="[A-Za-z0-9]"/>

The pattern attribute takes a normal regular expression syntax. Additionally, you can add the required (boolean) attribute, which indicates what a form submit will only work if the pattern is fulfilled.

<input type="text" pattern="[A-Za-z0-9]" required/>