JSFiddle - React, Tailwind, and code Playground

by Yuval Bar-On

HTML

<script>
    function verifyInput(txt, mask) { 
        var res = '';
        if (txt) {
            for (var i=0;i<txt.length;i++) {
                var char = txt[i];
                if (char in mask && res.indexOf(char) === -1)
                    res += char;
            }
        }
        return res;
    }
</script>

<input type="text" id="unique-numbers" oninput="this.value=verifyInput(this.value, [0, 1, 2, 3])" />