getTextContent function of PDF.js with sendWithStream

getTextContentStream.js

getTextContent: function PDFPageProxy_getTextContent(params) {
  var readableStream = this.transport.messageHandler.sendWithStream('GetTextContent', {
    pageIndex: this.pageNumber - 1,
    normalizeWhitespace: (params && params.normalizeWhitespace === true ?
                          true : /* Default */ false),
    combineTextItems: (params && params.disableCombineTextItems === true ?
                       false : /* Default */ true),
  });
  return new Promise(function (resolve, reject) {
    readAllChunks(readableStream);
    function readAllChunks (readableStream) {
      var reader = readableStream.getReader();
      var textContent = {
        items: [],
        styles: {}
      };

      pump();

      function pump () {
        reader.read().then(function (result) {
          if (result.done) {
            resolve(textContent);
          }
          if (typeof result.value[0] == 'string') {
            textContent.styles[result.value[0]] = result.value[1];
          } else {
            textContent.items.push(result.value[0]);
            if (result.value[1]) {
              textContent.items.push(result.value[1]);
            }
          }
          pump();
        }, function (error) {
          reject(error);
        });
      }
    }
  });
}