Array#lastIndexOf – fromIndex evaluation

Asen Bozhilov asen.bozhilov at
Sat Nov 3 12:28:38 PDT 2012

According to the spec if fromIndex is NaN or undefined the search will
start from 0. Step 5 of Array.prototype.lastIndexOf performs
This is in contradiction with String.prototype.lastIndexOf, where even if I
pass a NaN or undefined for position value, the search will start again
from the end of the string.
I am wondering what is the intention of that decision, because it seems
like bug in specification.
Thank you.
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