loop guard in while loop appears to be failing

[thetazero]

Version

v14.17.5

Platform

Linux XPS 5.15.0-58-generic nodejs/node#64-Ubuntu SMP Thu Jan 5 11:43:13 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux

Subsystem

No response

What steps will reproduce the bug?

Enter the node REPL then type

i = 0
while (i < 5) {
    console.log(i)
    i += 1
}

How often does it reproduce? Is there a required condition?

always seems to reproduce

What is the expected behavior?

Entering this code into a file, then executing it with node file.js gives the following output as expected

0
1
2
3
4

What do you see instead?

0
1
2
3
4
5

Additional information

No response

[jasnell]

This is an unfortunate artifact of the REPL... it always prints the results of the last statement when execution is complete. For instance, if we run the following in the REPL...

> (() => { let i = 0; while (i < 5) { console.log(i); i += 1 } })()

we get.

0
1
2
3
4
undefined

Note the undefined there...

In your example, the last line evaluated that produces a result is the i += 1 that increments i to 5, and therefore 5 ends up being printed. The loop is exiting correctly, it's just the result display looking off.

Another example, perhaps clearer:

> i = 0
0
> while (i < 5) { console.log('...', i); i += 1 }
... 0
... 1
... 2
... 3
... 4
5
>

[thetazero]

Interesting, thank you

[github-actions]

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