Self assignments like a = a; have no effect at all. If there are self assignments in the code, most likely it means that the author is still in the process of refactoring and there's remaining work they have to do.

Invalid:

a = a;
[a] = [a];
[a, b] = [a, b];
[a, b] = [a, c];
[a, ...b] = [a, ...b];
a.b = a.b;

Valid:

let a = a;
a += a;
a = [a];
[a, b] = [b, a];
a.b = a.c;