Const declares something to be constant. Can it mutate?
TL;DR: Don't rely on languages cheating about directives.
Unexpected side effects
Use better languages.
Use spread operator.
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, Oliver Jumpertz 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.
This article is part of the CodeSmell Series.