HTML

kak ispolzovat html checkbox

<input type="checkbox" onclick="checkFluency()"  id="fluency" checked />

kak ispolzovat html checkbox

function checkFluency()
{
  var checkbox=document.getElementById('fluency');
  if(checkbox.checked!=true)
  {
    alert("you need to be fluent in English to apply for the job");
  }
}