Shorten array by changing the length does not shorten the array in Espruino

[espruino-discuss]

Posted at 2023-06-11 by @MaBecker

Tested code in Emulator

a = [0,1,2,3,4]
//=[ 0, 1, 2, 3, 4 ]
a.length
//=5
a.length = 3
//=3
a
=[ 0, 1, 2, 3, 4, length: 3 ]
// should return >a = [0,1,2]

Tested code in Google Chrome

a = [0,1,2,3,4]
//(5) [0, 1, 2, 3, 4]
a.length
//5
a.length = 3
//3
a
//(3) [0, 1, 2]

Workaround in Espruino

a = [0,1,2,3,4]
//=[ 0, 1, 2, 3, 4 ]
a = a.slice(0,3)
//=[ 0, 1, 2 ]
a.length
//=3

[gfwilliams]

Posted at 2023-06-12 by @gfwilliams

Thanks - yes, that's something I've known about for a while. I was sure there was an issue on GitHub for it but I can't see it now!

Did you hit this when trying to run some existing code on Espruino?

I've just tweaked Espruino to ensure that length is at least returned as a constant, so while it's not compliant, at least code that uses it will now error.

[espruino-discuss]

Posted at 2023-06-12 by @MaBecker

Did you hit this when trying to run some existing code on Espruino?

No, just identified this in my personal code.