worker-eval.ts

const getWorkerMessenger = async () => {
    const polyfill = (await IE_POLYFILL).default;
    const sendMessage: IMessagePoster = (
      functionBody: string,
      args: unknown[] = [],
      callback: ICallback
    ) => {
      const blob = new Blob(
        [
          polyfill,
          '\n',
          'var window = self;\n',
          'function send(e, v, reportSendError){',
          'try {postMessage({value: v, error: e ? {name: e.name, message: e.message, stack: e.stack} : undefined});}',
          'catch (err) {if (reportSendError !== false) send(err, undefined, false);}',
          '}',
          'self.addEventListener("unhandledrejection", function(e){e.preventDefault();send(e.reason, undefined);});',
          'onmessage=function (evt){',
          'let result, error;',
          'try {\n',
          functionBody,
          '\n',
          `result=${CUSTOM_FUNCTION_NAME}.apply(undefined, evt.data);\n`,
          '} catch (err) {error = err;}\n',
          'if (!error && result && typeof result.then === "function") {\n',
          'result.then(',
          'function (r) {result = r;},',
          'function (e) {error = e;}',
          ').finally(function () {send(error, result);});\n',
          '} else {send(error, result);}\n',
          '}',
        ],
        {
          type: 'application/javascript',
        }
      );
  
      const workerURL = URL.createObjectURL(blob);
      const worker = new Worker(workerURL);
      const cleanup = () => {
        worker.terminate();
        // Release memory as we may have many and large functions
        URL.revokeObjectURL(workerURL);
      };
      worker.onmessage = ({ data: { value, error } }: { data: IResult }) => {
        cleanup();
        callback(error ? deserializeError(error) : undefined, value);
      };
  
      worker.onerror = (err) => {
        err.preventDefault();
        err.stopPropagation();
        cleanup();
        let error = err.error;
        if (!error) {
          error = deserializeError({
            name: 'SyntaxError',
            message: err.message,
            stack: `${err.message} at ${err.filename}:${err.lineno}:${err.colno}`,
          });
        }
        callback(error, undefined);
      };
  
      worker.postMessage(args);
    };
    sendMessage.type = 'worker';
    return sendMessage;
  };