spiritjs/lib/utils/jsonloader.js

The animation toolkit for the web

"use strict";

exports.__esModule = true;
exports.cache = void 0;
exports["default"] = _default;
exports.req = void 0;
var _context = require("./context");
var req = exports.req = {};
var cache = exports.cache = {};

/**
 * JSON Loader.
 * Optimize requests by caching results based on url.
 *
 * @param   {string} url
 * @returns {Promise}
 */
function _default(url) {
  // only run in browser
  if (!(0, _context.isBrowser)()) {
    return Promise.reject(new Error('Invalid context. jsonLoader can only be used in browser.'));
  }

  // serve from cache
  if (url in cache) {
    return Promise.resolve(cache[url]);
  }

  // serve from queued promise
  if (url in req) {
    return req[url];
  }

  // create promise request
  var promise = new Promise(function (resolve, reject) {
    var xmlhttp = new XMLHttpRequest();
    xmlhttp.onreadystatechange = function () {
      if (this.readyState === 4 && this.status === 200) {
        try {
          var result = JSON.parse(this.responseText);
          cache[url] = result;
          resolve(result);
          delete req[url];
        } catch (err) {
          reject(new Error("jsonLoader: Invalid json for request " + url));
        }
      }
    };
    try {
      xmlhttp.open('GET', encodeURI(url), true);
      xmlhttp.send();
    } catch (err) {
      reject(new Error("Could not open request. Unable to load " + url));
    }
  });

  // store request
  if (!req[url]) {
    req[url] = promise;
  }

  // send back the promise
  return promise;
}