Why call removeEventListener inside addEventListener callback?

Question

I have downloaded a JS starter template. It has a default.js file like this: (Of course the js file is referenced in an html page that contains just an <a> element.)

(function () {
    "use strict";
    window.addEventListener("load", function load(event) {
        window.removeEventListener("load", load, false);
        init();
    }, false);

    function init() {
        document.getElementById("link").addEventListener("click", showAlert, false);
    }

    function showAlert() {
        alert("Welcome to Pure HTML!");
    }
}());

Now my question is why there is a window.removeEventListener in the window.addEventListener function?

Answer 1

It is a pattern for allowing an event handler to execute once. In the first execution of the event handler, the event handler is removed to stop it executing again.

It's interesting this is used for the window load event, as that should only fire once anyway.