Alternatively, you can opt to not load an entire Javascript library for something as simple as this:

document.querySelector('#button').addEventListener('onclick', exit_alert);

You are binding the event handler inline in HTML also you are using jQuery to bind again inside the function which is not correct.

Just remove the inline onclick,

<input type="button" id="ImageHosting" value="To Image Hosting" />

And change JS

$(document).ready ( function () {
    $("#ImageHosting").click(function () {
       alert("test");
    });
});

Incase if this button is inserted dynamically then,

$(document).ready ( function () {
    //replace document below with enclosing container but below will work too
    $(document).on('click', "#ImageHosting", function () {
       alert("test");
    });
});

Use .live/.delegate if you older version of jQuery ( < 1.7)