Why doesn't assignment to Symbol.iterator throw an error?

Question

In Chrome on Windows, I have this in the console:

> Symbol.iterator
< Symbol(Symbol.iterator)
> Symbol.iterator = "Hello!";
< "Hello!"
> Symbol.iterator;
< Symbol(Symbol.iterator)

So Symbol.iterator (thankfully) doesn't change, but why doesn't my attempt to assign to it throw an error?

score 2 · Accepted Answer · answered Mar 04 '19 at 19:51

2

In sloppy mode, the failed assignment doesn't cause an exception. Use strict mode instead:

(function(){ "use strict"; Symbol.iterator = "Hello" }())

Uncaught TypeError: Cannot assign to read only property iterator of function function Symbol() { [native code] }

answered Mar 04 '19 at 19:51

Bergi

Even in "sloppy" mode, I never would have imagined they'd let something like that go! What a nightmare. – Green Grasso Holm Mar 11 '19 at 18:19

1 Answers1