JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://code.jquery.com/jquery-1.12.1.min.js"></script>
 <input type="Custom" name="donation-amount" class="inpt-first form-control" id="donation-amount" onclick="if(this.defaultValue == this.value) this.value = ''" onblur="if(this.value=='') this.value = this.defaultValue" value="Custom">

JavaScript

var defaultValue = 10; 

$(document).ready(function() {
      $('#donation-amount').keyup(function() {
        // check if numbers are type
        var reg = /^\d+$/;
      	if(reg.test($(this).val())) {
          $('#donation-amount').val($(this).val());
    		} else {
       	 $('#donation-amount').val(defaultValue);
   
    		}      
      });
});