JSFiddle - React, Tailwind, and code Playground

HTML

Login:<br /><input id="txtLogin" type="text" /><br />
PWord:<br /><input id="txtPassword" type="password" /><br />
<input type="button" id="mybutt1" value="One" />
<input type="button" id="mybutt2" value="Two" />
<input type="button" id="mybutt3" value="Three" />

Default button Number:<br /><input id="pickabutt" type="text" /><br />

JavaScript

var defaultbutt = 2;

$('[id^=txt]').blur(function() {
	if ($(this).val() != '') {
		defaultbutt = $('#pickabutt').val();
		if (defaultbutt=='') defaultbutt = 2;
	}
});

$('#pickabutt').blur(function() {
	defaultbutt = $('#pickabutt').val();
	if (defaultbutt=='') defaultbutt = 2;
});

$(document).keypress(function(e) {
	if(e.which == 13) {
		$('#mybutt' + defaultbutt).click();
	}
});

$('[id^=mybutt]').click(function() {
	var num = $(this).val();
	alert('You clicked button: ' + num);
});