print-perf-metrics.js

const timings = performance.getEntriesByType('navigation')[0]
const allEntries = performance.getEntries()
const customMetrics = allEntries
  .filter(entry => ['mark', 'measure'].includes(entry.entryType )) // array of PerformanceMark / PerformanceMeasure objects
  .reduce((final, current) => { // make an object
    final[current.entryType.toUpperCase() +  ' — ' + current.name] // key name : "MARK — loadInAsync que/query_grid_webpart start"
      = Math.round(
        current.entryType === 'measure' ? current.duration : current.startTime
      )
    return final // object with key looking like this "MARK — loadInAsync que/query_grid_webpart start" and value is number of milliseconds
  }, {})

// Pour Ivalua en mode DEV seulement
var jsTimer = document.getElementById('jsTimerSpan').innerText // ' +0,45'
  .split(ivScope.UserNumberFormat.NumberDecimalSeparator) // [' +0', '45']
  .map(Number) // [0, 45]
jsTimer = jsTimer[0] * 1000 + jsTimer[1] * 10 // 450 (en millisecondes)


const out = {
  'Time To First Byte':Math.round(timings.responseStart),
  'Server response time': Math.round(timings.responseStart - timings.requestStart),
  // 'Input Latency' ==> plus compliqué, demande de poser des listeners en début de page
  'First Paint': Math.round(allEntries.filter(entry => entry.name === 'first-paint')[0].startTime),
  'jsTimer' : jsTimer,
  // Visual Layout Stability ==> demande de poser des listeners en début de page
  // JS blocking time ==> demande de poser des listeners en début de page
  ...customMetrics
}

console.table(out)