JSFiddle - React, Tailwind, and code Playground

by naveen

HTML

<input id="invoice" type="text">
<button id="test">Test</button>

JavaScript

$("#test").on("click", function() {
    var rgx = /^\d{4}\/\d{2}$/;
    var error_message = "";
    var invoice_value = $.trim($("#invoice").val());
    if (invoice_value) {
        if (!invoice_value.match(rgx)) {
            error_message = "Please enter a valid invoice number";
        }
        else {
            error_message = "Valid invoice number!";
        }
    } else {
        error_message = "Please enter an invoice number";
    }
    alert(error_message);
});