移除的EventListener仍然会触发

Question

I have an event like so:

var CountDemKeys;
document.body.addEventListener('keypress', function() { 
  CountDemKeys++;
  if (CountDemKeys % 10 === 0) {
    alert("WOO HOO!");
  }
});

and in a separate function:

RemoveShizzle = function() {
  document.body.removeEventListener('keypress');
};

But the event still fires :(

note: I've also tried setting the event to null : document.body.addEventListener('keypress', null);

document.body.addEventListener('keypress', null);

no joy...

Answer 1

you have to pass the same function as the second argument to removeEventListener .

There could be other listeners attached to 'keypress' to the body element.

Thus, without supplying the original function, removeEventListener does not know which listener to remove.

var CountDemKeys;
var listener = function() { 
  CountDemKeys++;
  if (CountDemKeys % 10 === 0) {
    alert("WOO HOO!");
  }
};
document.body.addEventListener('keypress', listener);

RemoveShizzle = function() {
  document.body.removeEventListener('keypress', listener);
};

Answer 2

You're most probably missing the second argument of removeEventListener .

Also please note that for MSIE support, you would need to use attachEvent