Simple auto reload page on change, Live edit / Live preview

autoreload.js

//pretty dirty autoreload script
var lastMod = [];
var files = [window.location.href];
var countReq = 0;
var hidden = false;

function __autoreload() {
    var checkfiles = true;
    if (document.hasFocus()) {
        checkfiles = false;
        hidden = false;
    } else if (typeof document.hidden !== "undefined" && document.hidden === true) {
        checkfiles = false;
        hidden = true;
    } else if (typeof document.msHidden !== "undefined" && document.msHidden === true) {
        checkfiles = false;
        hidden = true;
    } else if (typeof document.webkitHidden !== "undefined" && document.webkitHidden === true) {
        checkfiles = false;
        hidden = true;
    }
    if (checkfiles) {
        hidden = false;
        countReq++;
        files.forEach(function (url, i) {
            var xhr = new XMLHttpRequest();
            xhr.open('HEAD', url);
            xhr.onload = function () {
                if (xhr.status === 200) {
                    var d = new Date(xhr.getResponseHeader("Last-Modified"));
                    if (typeof lastMod[i] !== "undefined") {
                        if (d.toString() !== lastMod[i].toString()) {
                            location.reload();
                        }
                    } else {
                        lastMod[i] = d;
                    }
                }
            };
            xhr.send();
        });
    } else if (hidden && countReq > 10) {
        location.reload();
    }
    setTimeout('__autoreload()', countReq > 10 ? 1000 : 250);
}

window.addEventListener('DOMContentLoaded', function () {
    // add stylesheet
    for (let file of document.styleSheets) {
        if (typeof file !== "undefined" && file.href.indexOf(window.location.protocol + '//' + window.location.hostname) !== -1) {
            files.push(file.href);
        }
    }

    //add scrtipts files
    for (let file of document.scripts) {
        if (typeof file !== "undefined" && file.src.indexOf(window.location.protocol + '//' + window.location.hostname) !== -1) {
            files.push(file.src);
        }
    }

    __autoreload();
}, false);