Array.prototype.flatMap() JS is behaving strangely in test cases and a repl.it snippet, but not in browser console

Question

My apologies if this is a rookie question, but I've stumbled upon a puzzle.

Why would a JS standard function work in the chrome browser console, but not in an electron react project jest test case, or even in a repl.it snippet? Could it be a chromium thing?

The tests were passing last time I ran them a couple of weeks ago (back in 2019) The code affecting the tests hasn't been touched, (I'm fairly certain), but the project has been rebuilt recently.

This is the simple example from MDN

 let arr1 = [1, 2, 3, 4]; arr1.flatMap(x => [x * 2]); // [2, 4, 6, 8] console.log(arr1.flatMap(x => [x * 2]));

If you run the above, you will see the the SO compiler is fine with it.

BUT if I access it from a jest test case for an electron react app, it kerplunks:

It works fine in the browser console:

But it does not work in a repl .it snippet:

My guess would be that it is some kind of chromium thing. But I'm not sure how to confirm that.

Could somebody please direct me to the correct resource where I could learn more about this?

Answer 1

因为测试使用的是你电脑上安装的 node.js 版本，升级到第 12 个版本，你的版本中还没有提供 flatMap