It turns out that IE11 has a horrible bug whereby setting the
placeholder attribute before setting the text will trigger an input
event:
https://social.msdn.microsoft.com/Forums/ie/en-US/ae4832b0-8eee-4729-b93
3-a9977ea1b583/internet-explorer-input-event-get-fired-when-settingunset
ting-the-placeholder?forum=iewebdevelopment