PhpStorm - JavaScript function parameter IDE error

Question

I am trying to build a reusable JavaScript function that makes use of default parameters. However, the IDE warns me I do something wrong.

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Answer 1

You can switch the version here:

1. Press CTRL+ALT+S

2 Search for JavaScript & click the select field. and then select ECMAScript 6

Answer 2

In Preferences->Languages & Frameworks->JavaScript, select "ECMAScript 6" from the language version menu to be able to use the new syntax features of ES6.