function updateSize() { let nBytes = 0, oFiles = this.files, nFiles = oFiles.length; for (let nFileId = 0; nFileId 1; nApprox /= 1024, nMultiple++) { sOutput = nApprox.toFixed(3) + " " + aMultiples[nMultiple] + " (" + nBytes + " bytes)"; } // end of optional code document.getElementById("fileNum").innerHTML = nFiles; document.getElementById("fileSize").innerHTML = sOutput; } document.getElementById("uploadInput").addEventListener("change", updateSize, false);