Array.filter 也能够 map 对象数组是否正常？

Question

Not sure if this is really a question but I noticed this when I accidentally didn't use an equality check when using Array.filter. Instead, it mapped my array when I feel like I should've received some kind of error for not using the equality check:

const x = [{ name: 'user' }];
console.log(x.filter(x => x.name = 'another user'))

// Result:
// [{ name: 'another user' }]

Is this documented anywhere? I feel like this isn't intended. I couldn't find anything about Array.filter also being able to map so that's why I ask it here. Maybe this belongs on github...

Answer 1

There are many array methods which may well iterate over all elements of the array unless stopped earlier somehow (such as through a thrown error, or through a falsey value returned by the callback to Array.every , or through a truthy value returned by the callback to Array.find ).

These methods can all be misused to do something they weren't designed for. There are no exceptions, except perhaps for the generic iteration methods which were designed for side-effects.

Yes, you can misuse .filter as a substitution for a generic iteration method by performing side-effects inside the callback. You can also, for example, misuse .map the same exact way.

If you want to be able to protect yourself against these sorts of typos, consider using a linter which will warn you against it - such as with ESLint's no-return-assign .