如何测试Javascript实例并相应地创建一个HTML元素?

Question

我知道你可以使用链接到HTML代码的函数激活Javascript，如下所示：

<input type="button" id="foo">
<br>
<script>
document.getElementById("foo").addEventListener("click", thisFunction);
thisFunction() {
blah blah blah
}
</script>

但是，是否有可能测试javascript实例，然后创建一个HTML元素，本质上相反？有点像这样：

<script>
if (i = 0) {
create HTML header
}
</script>

我是JS和HTML的新手，所以如果它是一个简单的响应，请不要发疯。 谢谢你的帮助！

完整的JS：

function myAeroMexicoVacations(cb) {
aeroMexicoVacationsChecked = cb.checked ? 1 : 0;
alert(aeroMexicoVacationsChecked + "Aero Mexico Vacations");  
}
function myAllInclusiveOutlet(cb) {
allInclusiveOutletChecked = cb.checked ? 1 : 0;
alert(allInclusiveOutletChecked + "All Inclusive Outlet");  
}
function myBookit(cb) {
bookitChecked = cb.checked ? 1 : 0;
alert(bookitChecked + "BookIt");  
}
function myCheapCarribean(cb) {
cheapCarribeanChecked = cb.checked ? 1 : 0;
alert(cheapCarribeanChecked + "Cheap Carribean");  
}
function myCheapTickets(cb) {
cheapTicketsChecked = cb.checked ? 1 : 0;
alert(cheapTicketsChecked + "Cheap Tickets");  
}
function myDeltaVacations(cb) {
deltaVacationsChecked = cb.checked ? 1 : 0;
alert(deltaVacationsChecked + "Delta Vacations");  
}
function myExpedia(cb) {
expediaChecked = cb.checked ? 1 : 0;
alert(expediaChecked + "Expedia");  
}
function myFunJet(cb) {
funJetChecked = cb.checked ? 1 : 0;
alert(funJetChecked + "FunJet");  
}
function myOrbitz(cb) {
orbitzChecked = cb.checked ? 1 : 0;
alert(orbitzChecked + "Orbitz");  
}
function myTravelocity(cb) {
travelocityChecked = cb.checked ? 1 : 0;
alert(travelocityChecked + "Travelocity");  
}
function myUnitedVacations(cb) {
unitedVacationsChecked = cb.checked ? 1 : 0;
alert(unitedVacationsChecked + "United Vacations");  
}
function myVacationExpress(cb) {
vacationExpressChecked = cb.checked ? 1 : 0;
alert(vacationExpressChecked + "Vacation Express");  
}
var header = document.createElement('H1');
var body = document.getElementsByTagName('body');
body[0].appendChild("Hello");

Answer 1

function myFunction() { 
var header = document.createElement('H1');
var body = document.getElementsByTagName('BODY');
var textnode = document.createTextNode('Hello'); 
header.appendChild(textnode);
body[0].appendChild(header); 
}

这将告诉你你需要知道的：https://www.w3schools.com/jsref/dom_obj_all.asp，或者你可以使用MDN网站，这也是非常好的：https://developer.mozilla.org/en-US/docs/Web/API/Element。