utility.js

export async function loadAll(urls) {
  return new Promise(resolve => {
    let counter = urls.length;
    let resHash = {};
    urls.forEach(function (url) {
      if (url.toLowerCase().match(/(\.png$)|(\.bmp$)|(\.jpg$)|(\.jpeg$)/)) {
        let img = new Image();
        img.onload = function () {
          counter--;
          resHash[url] = img;
          if (counter === 0) {
            resolve(resHash);
          }
        };
        img.src = url;
      } else {
        let req = new XMLHttpRequest();
        req.addEventListener("load", function (res) {
          counter--;
          resHash[url] = res.target.responseText;
          if (counter === 0) {
            resolve(resHash);
          }
        });
        req.addEventListener("error", function () {
          counter = -1;
        });
        req.open("GET", url, true);
        req.send();
      }
    });
  });
}

export async function getText(path) {
  return new Promise(resolve => {
    let req = new XMLHttpRequest();
    req.addEventListener("load", function (res) {
      resolve(res.target.responseText);
    });
    req.open("GET", path, true);
    req.send();
  });
}

export function uploadDataUrl(path, blob, callback) {
  let req = new XMLHttpRequest();
  req.addEventListener("load", function (res) {
    callback.apply(null, [res]);
  });
  req.open("POST", path, true);
  req.send(blob);
}