Detect Page Speed with javascript

gistfile1.txt

// Taken from https://github.com/guardian/frontend/blob/5f9c1dcbb2c4270fb356711b1091d3fff7844a72/common/app/assets/stylesheets/components/pasteup/js/modules/detect.js

function getPageSpeed() {
    var start_time,
        end_time,
        total_time;

    var perf = window.performance || window.msPerformance || window.webkitPerformance || window.mozPerformance;
    if (perf && perf.timing) {
        start_time =  perf.timing.requestStart || perf.timing.fetchStart || perf.timing.navigationStart;
        end_time = perf.timing.responseStart;

        if (start_time && end_time) {
            total_time = end_time - start_time;
        }
    }

    return total_time;
}

function getConnectionSpeed() {

    var load_time = getPageSpeed();

    // Assume high speed for non supporting browsers.
    var speed = "high";

    if (load_time) {
        if (load_time > 1000) { // One second
            speed = 'medium';
            if (load_time > 4000) { // Four seconds
                speed = 'low';
            }
        }
    }
    
    return speed;
}


function getPixelRatio() {
    return window.devicePixelRatio;
}