Get PDF page count from a PDF Blob

getPdfPageCount.ts

/**
 * Get PDF page count from a PDF Blob
 *
 * Source: https://stackoverflow.com/a/58089003
 */
export const getPdfPageCount = (pdfFile: Blob) =>
  new Promise<number>((resolve, reject) => {
    const reader = new FileReader();

    reader.readAsBinaryString(pdfFile);

    reader.addEventListener("loadend", function () {
      if (!this.result) {
        resolve(0);
        return;
      }

      const count = (this.result as string).match(/\/Type[\s]*\/Page[^s]/g)?.length;

      if (!count) {
        resolve(0);
        return;
      }

      resolve(count);
    });

    reader.addEventListener("error", function () {
      reject("Failed to read PDF file during read of page count");
    });
  });