Crossbrowser onbeforeunload?

Question

Does window.onbeforeunload() fire in all browsers? I need a onbeforeunload functionality which is supported at least by IE6 and FF3.6.

For IE, onbeforeunload() seems only to be supported by IE9

Answer 1

I found a workaround for Firefox with setTimeout function because it does not have the same behaviour as other web browsers.

window.onbeforeunload = function (e) {
    var message = "Are you sure ?";
    var firefox = /Firefox[\/\s](\d+)/.test(navigator.userAgent);

    if (firefox) {
        //Add custom dialog
        //Firefox does not accept window.showModalDialog(), window.alert(), window.confirm(), and window.prompt() furthermore
        var dialog = document.createElement("div");
        document.body.appendChild(dialog);
        dialog.id = "dialog";
        dialog.style.visibility = "hidden";
        dialog.innerHTML = message; 
        var left = document.body.clientWidth / 2 - dialog.clientWidth / 2;
        dialog.style.left = left + "px";
        dialog.style.visibility = "visible";  
        var shadow = document.createElement("div");
        document.body.appendChild(shadow);
        shadow.id = "shadow";       
        //tip with setTimeout
        setTimeout(function () {
            document.body.removeChild(document.getElementById("dialog"));
            document.body.removeChild(document.getElementById("shadow"));
        }, 0);
    }

    return message;
}

GitHub: https://github.com/Aelios/crossbrowser-onbeforeunload