Record Page Load Time UserScript

record-page-load-time.js

// ==UserScript==
// @name         RPLT
// @description  Records page load times
// @author       ayubatif
// @match        https://YOUCANADDYOURDESIREDPATHHERE.OK/*
// ==/UserScript==
/**
 * Records page load time after response end. Saves a cookie for time data and sample number.
 * Once data collection complete, time data is saved to a local file.
 */
function dataCollection() {

  // Change NUM_SAMPLES according to your experiment
  const NUM_SAMPLES = 50;
  
  /**
  * cn: cookie name
  */
  function getCookie(cn){
    return new Promise((resolve) => {
      let n = cn + "=";
      let dc = decodeURIComponent(document.cookie);
      let ca = dc.split(';');
      for(var i = 0; i <ca.length; i++) {
        let c = ca[i];
        while (c.charAt(0) == ' ') {
          c = c.substring(1);
        }
        if (c.indexOf(n) == 0) {
          resolve(c.substring(n.length, c.length));
        }
      }
      resolve((cn == "n")? 0 : "");
    });
  }
  
  /**
  * cn: cookie name; x: cookie data; min: minutes to expiry
  */
  function setCookie(cn, x, min) {
    return new Promise((resolve) => {
      let d = new Date();
      d.setTime(d.getTime() + (min*60*1000));
      let expiry = "expires="+ d.toUTCString();
      document.cookie = cn + "=" + x + ";" + expiry + ";path=/";
      resolve();
    });
  }
  
  /**
  * converts 'b' in string to '\n' and returns a new string
  * x: string containing 'b'
  */
  function b2newline(x){
    return x.split('b').join('\n').substring(1,x.length);
  }
  
  function download(filename, text) {
    var element = document.createElement('a');
    element.setAttribute('href', 'data:text/plain;charset=utf-8,' + encodeURIComponent(text));
    element.setAttribute('download', filename);
    element.style.display = 'none';
    document.body.appendChild(element);
    element.click();
    document.body.removeChild(element);
  }
  
  function recordPageLoadTime(){
    return new Promise((resolve) => {
      window.addEventListener("load", function measureLoadTime() {
        window.removeEventListener("load", measureLoadTime);
        setTimeout(function() {
          let t = performance.timing;
          let loadTime = t.loadEventEnd - t.responseEnd;
          resolve(loadTime);
        }, 0);
      });
    });
  }
  
  recordPageLoadTime().then(t=>{
    let complete = false;
    let ts = "";
    /* append page load to previous samples */
    tp = getCookie("t").then(tvals => {
      ts = tvals.concat('b'+t)
      setCookie("t",ts,10);
    });
    /* update sample number and check for completion */
    np = getCookie("n").then(nval => {
      let n = parseInt(nval,10);
      complete = (n>NUM_SAMPLES-1)? true : false;
      setCookie("n",n+1,10);
    });
    /* download if done or reload for next sample */
    Promise.all([tp,np]).then(() => {
      if(complete) {
        results = b2newline(ts)
        console.log(results);
        download(window.location.hostname+"-pageloadtimes.txt", results);
      }
      else location.reload(true);
    });
  });

};

dataCollection();