JSFiddle - React, Tailwind, and code Playground

HTML

<input id="cno" maxlength="8" />

JavaScript

$('#cno').keypress( function(evt) {
var nvVal = $(this).val();
		var nvValLng = nvVal.length;
    if(nvValLng<=1) {
    alert('dfdf');
			if (!this.value.match(/[A-Z]/))  {
				evt.returnValue = false;
				return false;
			}
		} else {
			if (!this.value.match(/[0-9]/))  {
				evt.returnValue = false; 
				return false;
			}
		}
});