如何测试一个Javascript实例并相应地创建一个HTML元素？

Question

我知道你可以激活使用Javascript功能链接到HTML代码：

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

是否有可能，虽然，要测试一个javascript实例，然后创建一个HTML元素，本质上是相反的？有点像这样：

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

我是新来的JS和HTML，所以请不要发疯，如果它是一个简单的回应。感谢您的帮助！

完全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); 
} 

这会告诉你你需要知道：https://www.w3schools.com/jsref/dom_obj_all.asp，或者您可以使用MDN网站，这也很不错：https://developer.mozilla.org/en-US/docs/Web/API/Element。