JSFiddle - React, Tailwind, and code Playground

JavaScript

let sampleData = Array.from({length: 100}, () => Math.floor(Math.random() * 20));
console.log("SampleData: " + sampleData)

let meanMaxByTimeFrame = [];

let start = performance.now();

let sampleDataLength = sampleData.length;
let sampleDataMaxIndex = sampleDataLength;
let sumArray = [];

for(var intervalInSeconds = 1; intervalInSeconds <= sampleDataLength; intervalInSeconds++){
  let allAveragesForCurrentInterval = [];
  for(var sampleDataIndex = 0; sampleDataIndex < sampleDataMaxIndex; sampleDataIndex++){
    sumArray[sampleDataIndex] =  sampleData[sampleDataIndex+intervalInSeconds-1] + ((intervalInSeconds === 1) ? 0 : sumArray[sampleDataIndex]);
    let avg =  sumArray[sampleDataIndex]/intervalInSeconds;
    allAveragesForCurrentInterval.push(avg);
  }
  meanMaxByTimeFrame.push({'Interval': intervalInSeconds, 'MeanMax': Math.max.apply(Math, allAveragesForCurrentInterval)});
  sampleDataMaxIndex--;
}

console.log(meanMaxByTimeFrame)

let time = performance.now();
console.log('Duration: ' + (time - start) + ' ms.');