spankalee on Safe Assignment

The real safe assignment that I want to see is for optional chaining to be valid in LHS of assignments:

    foo?.bar = 42;

This would not perform the assignment if an optionally chained value was nullish. It downlevels to

    foo == null ? undefined : foo.bar = 42;

Given that the assignment is a SyntaxError now, this should be possible.

You can avoid the SyntaxError by abusing boolean expressions a bit:

  > obj = {}
  {}
  > obj != null && (obj.bar = 42)
  42
  > obj
  { bar: 42 }

Not as pretty as your LHS case, but it works.

With the length of that you might as well do:

    if (obj) obj.bar = 42

Would it evaluate the RHS? It feels like it shouldn’t, but somehow that seems weird too.

Comments