JavaScript

JavaScript closures can be kind of weird. The way a closure works within a loop is a fairly common "gotcha" because it doesn't work in the way that it intuitively feels like it should.

Take the following block of code:

for (var i = 0; i < 5; i++) {
    var button = document.createElement("button");
    button.innerHTML = "Button #" + (i + 1);
    button.onclick = function() {
        alert("You clicked on " + button.innerHTML + "!");
    };
    document.body.appendChild(button);
    document.body.appendChild(document.createElement('br'));
}

What does that do? Read More to find out.