Is it possible to configure a required field to ignore white space?

Question 1

Use the pattern attribute combined with the required attribute. And be sure to include a title attribute as well, since most browsers insert the title text into the validation pop-up bubble.

<input required pattern=".*\S+.*" title="This field is required">

The .*\S+.* pattern requires at least one non-whitespace character, but also allows whitespace characters (spaces, tabs, carriage returns, etc.) at the beginning or end. If you don't want the user to be able to put whitespace at the beginning/end, then use this instead:

<input required pattern="\S+" title="This field is required">

Question 2

Try the pattern attribute. You'll need a regex which specifies 'at least one character'.

Question 3

You probably want this:

<input type="text" required pattern="\S(.*\S)?">

(At least one non-whitespace character and no whitespace at the beginning or end of the input)

Or if whitespace at the beginning and end are fine, then this:

<input type="text" required pattern=".*\S.*">

Question 4

step 1

create a Javascript function:

function ignoreSpaces(event) {
  var character = event ? event.which : window.event.keyCode;
    if (character == 32) return false;
}

Step 2

use it on any text-input field in HTML.

<input type="text" id="userInput" onkeypress="return ignoreSpaces(event)">

Working example :

index.html

<html> 
<body>
  <input type="text" onkeypress="return ignoreSpaces(event)">
  
  <script>
    function ignoreSpaces(event) {
        var character = event ? event.which : window.event.keyCode;
        if (character == 32) return false;
    }
  </script>

</body>
</html>