JSFiddle - React, Tailwind, and code Playground

HTML

<body>
    <script>
      function numbersOnly(oToCheckField, oKeyEvent) {        
        var s = String.fromCharCode(oKeyEvent.charCode);
        var containsDecimalPoint = /\./.test(oToCheckField.value);
        return oKeyEvent.charCode === 0 || /\d/.test(s) || 
            /\./.test(s) && !containsDecimalPoint;
      }
    </script>
    <form name="myForm">
        <p>Enter numbers (one decimal point allowed):
            <input type="text" name="myInput" onkeypress="return numbersOnly(this, event);" onpaste="return false;" />
        </p>
    </form>
</body>