getElementsByName()

js/script.js

function funChange() {
if(document.getElementsByName('txt1')[0].innerHTML == 'Hello World!' && document.getElementsByName('txt2')[0].innerHTML == 'Привет Мир!') {
document.getElementsByName('txt1')[0].innerHTML = 'Привет Мир!';
document.getElementsByName('txt2')[0].innerHTML = 'Hello World!'
}
else {
document.getElementsByName('txt1')[0].innerHTML = 'Hello World!';
document.getElementsByName('txt2')[0].innerHTML = 'Привет Мир!'
}
}
window.onload = function() {
document.getElementById('b1').onclick = funChange;
}

function funChange() {
if(document.getElementsByName('txt1')[0].innerHTML == 'Hello World!' && document.getElementsByName('txt2')[0].innerHTML == 'Привет Мир!') {
document.getElementsByName('txt1')[0].innerHTML = 'Привет Мир!';
document.getElementsByName('txt2')[0].innerHTML = 'Hello World!'
}
else {
document.getElementsByName('txt1')[0].innerHTML = 'Hello World!';
document.getElementsByName('txt2')[0].innerHTML = 'Привет Мир!'
}
}
window.onload = function() {
document.getElementById('b1').onclick = funChange;
}

index.html