fix: throw error if URL is provided but fetch is not available

Author: mojoaxel

PDFMergerBase.js

@@ -162,6 +162,9 @@ export default class PDFMergerBase {
 
     // see https://developer.mozilla.org/en-US/docs/Web/API/URL
     if (input instanceof URL) {
+      if (typeof fetch === 'undefined') {
+        throw new Error('fetch is not defined. You need to use a polyfill for this to work in Node.js.')
+      }
       const res = await fetch(input)
       const aBuffer = await res.arrayBuffer()
       return new Uint8Array(aBuffer)

test/PDFMerger.test.js

@@ -121,7 +121,8 @@ describe('PDFMerger', () => {
       expect(diff).toBeFalsy()
     })
 
-    test('provide input as URL', async () => {
+    const testIfFetch = typeof fetch !== 'undefined' ? test : test.skip
+    testIfFetch('provide input as URL', async () => {
       const merger = new PDFMerger()
       const TestfileAURL = new URL('https://raw.githubusercontent.com/nbesli/pdf-merger-js/master/test/fixtures/Testfile_A.pdf')
       expect(TestfileAURL).toBeInstanceOf(URL)