HTML simple not blank pattern

Question

I have a simple form and i want the submit button not to work for the conditions i give in the pattern, but if i leave it blank the submit works. how can i make the pattern not to accept it if it is blank?

<form action="test.php" method="POST"> Enter user name:  <input type="text" name="username" pattern="[A-Za-z0-9]{1,20}"> <input type="submit" value="submit"> </form> 

I thought the {1,20} is enought but it seems it's not.

Answer 1

HTML has the required attribute to accomplish this. If you set any input to be required, modern browsers won't let you submit the form if those fields are empty.

<input type="text" name="username" required="required" pattern="[A-Za-z0-9]{1,20}"> 

Answer 2

To prevent errors from showing on load, you can not use the HTML5 required attribute. You can use JavaScript. For example:

if ( $('#form-password').val() === "" )  {     e.preventDefault(); } 

Using HTML Patterns to match at least one:

<input type="text" name="username" pattern=".{1,}">