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Puppeteer Evaluation failed: ReferenceError: __awaiter is not defined


Oct 24 2020 at 20:10 GMT

I am using Puppeteer with TypeScript and when I try to evaluate an async function on a page:

await page.evaluate(async function() {
  // code to execute on the page

I get the following error:

Error: Evaluation failed: ReferenceError: __awaiter is not defined

What is causing this? How can I fix the issue?

1 Answer


Oct 24 2020 at 20:30 GMT

It looks like TypeScript is transpiling your code to an older version of JavaScript and so the async function is converted to code that is using the __awaiter util.

However, Puppeteer serializes the function passed to page.evaluate into a string and tries to execute it in the browser.

Since the __awaiter helper was not sent to the browser, you get a ReferenceError.

The solution is to not transpile your code to something old like ES5 as it's not really necessary; Puppeteer runs in one of the latest versions of Chrome, which supports modern JavaScript features, and this is also the case for a modern version of NodeJS.

So, to make the TypeScript compiler not transform async functions, you need to change the in tsconfig.json to at least ES2017:

  "compilerOptions": {
    "target": "ES2017",
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