jquery - Cannot use jquery event on woff?

Question

I'm building a website using bootstrap and fontawesome. And now I want to use JQuery onclick event on an icon-plus icon. But nothing happened after I click the icon. I found some bootstrap examples who can work right and saw that browser download icon as png. But fontawesome provides icon as woff. My jquery code as follow:

$(".icon-plus").on("click",function(e){
  $("#form").append(...);
});