Problems

Solutions

const array = [1, 2];

array.push(3)

//array => [1, 2, 3]
//Wasn't it constant ?
//constant != immutable ?

const array = [1, 2];

const newArray = [...array,3 ]

//array => [1, 2] Didn't mutate
//newArray = [1, 2, 3]

Since this is a "language feature", we can explicitly forbid it.

We should always favour immutability on our designs and take extra care with side effects.

Thank you, @oliverjumpertz for this tip.

Correctness is clearly the prime quality. If a system does not do what it is supposed to do, then everything else about it matters little.

Bertrand Meyer

This article is part of the CodeSmell Series.