Should you use map for side effects in JavaScript?
No. If you do not need the returned array, use forEach instead. Using map for side effects wastes the returned array and is misleading (it signals transformation when you only want iteration).
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More FAQs in map in JavaScript: Examples and Use Cases
It calls a callback on each element of the array and returns a new array with the results. The new array has the same length as the original. The original array is not mutated.
Use map with a callback that returns the property: users.map(u => u.name). This returns a new array of just the names.
Use spread to create a new object with the added property: users.map((u, i) => ({ ...u, id: i + 1 })). Do not mutate the original object.
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