script to read/write a file that is stored in a local "dropbox" folder or a local "google drive"

Question

For the moment, the dropbox API allows a browser to access (read/write) all type of files in a dropbox folder on your local drive by script. The file path and name can be specified in the script. The script works on webpages that are stored on a local drive, but also works on webpages that are stored on a remote site when using Chrome.

Please see these jsfiddles with a primitive implementation to test writing and reading a text file in a local dropbox folder. The scripts are written in pure vanilla javascript code, and no not need a library. Only a one-time access token is needed and no further authentication procedure.

This jsfiddle (click) demonstrates: Write text file to local dropbox folder

function WriteFile() {
  var H = new Array(6);
  H[0] = "Authorization";
  H[1] = document.getElementById("bear").value;
  H[2] = "Content-type";
  H[3] = "application/octet-stream";
  H[4] = "Dropbox-API-Arg";
  H[5] = '{"path": "/' + document.getElementById("pana").value;
  H[5] = H[5] + '","mode":{".tag":"overwrite"}}';
  var X = new XMLHttpRequest();
  X.onreadystatechange = acb;
  X.open("POST", "https://content.dropboxapi.com/2/files/upload", true);
  X.setRequestHeader(H[0], H[1]);
  X.setRequestHeader(H[2], H[3]);
  X.setRequestHeader(H[4], H[5]);
  X.send(document.getElementById("myText").value);
  document.getElementById("demo").innerHTML = "writing . . .";
}

function acb(A) {
  var X = A.target;
  var G = X.readyState;
  if (G != 4) {
    return 0;
  }
  document.getElementById("demo").innerHTML = "status: " + X.status;
}

This jsfiddle (click) demonstrates: Read text file from local dropbox folder

function ReadFile() {
  document.getElementById("text").value = "";
  var H = new Array(6);
  H[0] = "User-Agent";
  H[1] = "api-explorer-client";
  H[2] = "Authorization";
  H[3] = document.getElementById("bear").value;
  H[4] = "Content-type";
  H[5] = "application/json";
  var X = new XMLHttpRequest();
  X.onreadystatechange = acb;
  X.open("POST", "https://api.dropboxapi.com/2/sharing/create_shared_link", true);
  X.setRequestHeader(H[0], H[1]);
  X.setRequestHeader(H[2], H[3]);
  X.setRequestHeader(H[4], H[5]);
  X.send('{"path": "/' + document.getElementById("pana").value + '"}');
  document.getElementById("stat").innerHTML = "Reading . . .";
}
// async call back 1
function acb(A) {
  var X = A.target;
  if (X.readyState != 4) {
    return 0; // when ready
  }
  var stat = X.status;
  document.getElementById("stat").innerHTML = "status: " + stat;

  if (stat != 200) {
    document.getElementById("text").value = "NOT FOUND";
    return 0; // error
  }
  var B = X.responseText;
  var C = JSON.parse(B);
  var D = C.url;
  var E = D.split(".com");
  var F = E[1];
  var G = "https://dl.dropboxusercontent.com" + F;
  document.getElementById("text").value = G;
  X = new XMLHttpRequest();
  X.onreadystatechange = acb2;
  X.open("GET", G, true);
  X.send(null);
}
// async callback 2
function acb2(A) {
  var X = A.target;
  if (X.readyState != 4) {
    return 0; // when ready
  }
  var stat = X.status;
  if (stat != 200) {
    document.getElementById("text").value = "Can't Read the file";
    return 0; // error
  }
  var B = X.responseText;
  document.getElementById("text").value = B;
}

I tried to obtain the same functionality for files in a "google drive" on a local drive , using the "google drive API", but without success. Can someone achieve this, eventually using other cloud storage systems.