Strange result of String.fromCharCode

[espruino-discuss]

Posted at 2019-03-17 by Steffen

String.fromCharCode seems to return strange values for codes below 8:
String.fromCharCode(8) -> "\b" (OK) String.fromCharCode(7) -> "\713" (???)
Although String.fromCharCode(7).length returns 1 it doesn't seem to be the same as "\x07".
What's going on here?

[espruino-discuss]

Posted at 2019-03-17 by Robin

Sun 2019.03.17

@steffen, what version of Espruino is flashed and on which device?

process.env

Please post

[espruino-discuss]

Posted at 2019-03-17 by Steffen

process.env
={
VERSION: "2v01",
GIT_COMMIT: "748a4d3",
BOARD: "ESPRUINOWIFI",
FLASH: 524288, RAM: 131072,
SERIAL: "65005000-0b513532-39333638",
CONSOLE: "USB",
MODULES: "Flash,Storage,hea" ... ",neopixel,Wifi,AT",
EXPTR: 536871128 }

[gfwilliams]

Posted at 2019-03-18 by @gfwilliams

Please could you provide the exact code that gives you the error? I just tried this and it works fine for me with identical firmware on the same device:

>process.env
={
  VERSION: "2v01",
  GIT_COMMIT: "748a4d3",
  BOARD: "ESPRUINOWIFI",
  FLASH: 524288, RAM: 131072,
  SERIAL: "3d002100-0b513532-39333638",
  CONSOLE: "USB",
  MODULES: "Flash,Storage,hea" ... ",neopixel,Wifi,AT",
  EXPTR: 536871128 }
>String.fromCharCode(7)
="\7"

[espruino-discuss]

Posted at 2019-03-18 by Steffen

You are right, it works perfectly well on a clean device.
It seems like passing a wrong argument (the '\x07' string) causes the error:

>String.fromCharCode('\x07')  // wrong argument, but no complaint
="\0FD"
>String.fromCharCode(7)     // correct argument, but extra chars
="\7FD"
>String.fromCharCode(8)    // correct argument (above 8 every value gives the correct result)
="\b"
>String.fromCharCode(7)    // correct argument below 8, always with extra chars
="\7FD"

(It was pretty hard to find out how to reproduce the effect.)

[gfwilliams]

Posted at 2019-03-19 by @gfwilliams

Wow, thanks for narrowing this down. Turns out it's to do with outputting a hex value under 32 but above 7, and THEN outputting under 8.

This reliably does it:

>String.fromCharCode(0x1f)
="\x1F"
>String.fromCharCode(7)
="\71F"

It's just been fixed!