var popup = "something..."

var popups = [];

// Add with .push()
popups.push("something");
popups.push("something else");

// Remove with .splice()
// to remove the first element popups[0]
popups.splice(0, 1);

popups.push("third thing");
popups.push("fourth thing");

console.log(popups);
// ["something else", "third thing", "fourth thing"]

// Remove the current second item popups[1]
popups.splice(1,1);

console.log(popups);
// ["something else", "fourth thing"]

for (var i=0; i<popups.length; i++) {
  if (popups[i] === valueToRemove) {
    popups.splice(i, 1);
  }
}