ESLint: Assignment to property of function parameter 'element' (no-param-reassign)

Asked Nov 03 '16 at 16:50

Active Nov 03 '16 at 16:55

Viewed 603 times

export const displayElement = (element) => element.style.display = 'block';

Error:

Assignment to property of function parameter 'element' (no-param-reassign).

This is a setting from the airbnb eslint. Thing is, I'm not sure how to accomplish this. What would be the recommended way to assign the style property?

asked Nov 03 '16 at 16:50

babbaggeii

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What does no-param-reassign mean? – guest271314 Nov 03 '16 at 16:52
It's a setting on eslint that is saying that I'm trying to reassign a property on a function parameter. – babbaggeii Nov 03 '16 at 16:54
Why would assigning or reassigning a property on a function parameter cause a warning? – guest271314 Nov 03 '16 at 17:11
@guest271314 It's considered a good practice not to mutate function parameters. – Michał Perłakowski Nov 03 '16 at 17:18
@Gothdo only in functional languages... – Alnitak Nov 03 '16 at 17:29
@Gothdo Do you mean that parameters passed to functions should not be overwritten or changed? Link to documentation describing the considerations and practices of handling function parameters? – guest271314 Nov 03 '16 at 17:30
@Alnitak JavaScript can be written in functional style. – Michał Perłakowski Nov 03 '16 at 17:35
@guest271314 Documentation doesn't say anything about it, because it's rather a matter of style. It isn't an official recommendation. – Michał Perłakowski Nov 03 '16 at 17:37
@Gothdo Where did you find a description of the style pattern recommending to not change function parameters? – guest271314 Nov 03 '16 at 17:39
@guest271314 https://github.com/airbnb/javascript#functions--mutate-params – Michał Perłakowski Nov 03 '16 at 17:40
@Gothdo sure, it can, but unlike most real functional languages variables in JS *are* mutable, and setters are called implicitly (if required) when you set the value of a property, so there's usually no need for objects to expose explicit "obj.setSomeProperty(newValue)` calls. – Alnitak Nov 03 '16 at 17:42
@Gothdo What are examples of "unwanted variable side effects" and "unexpected behavior"? – guest271314 Nov 03 '16 at 17:44

ESLint: Assignment to property of function parameter 'element' (no-param-reassign)

0 Answers0