Why does Array.prototype.push return the new length instead of something more useful?

Question

Ever since its introduction in ECMA-262, 3rd Edition, the Array.prototype.push method\'s return value is a Number:

Answer 1

I posted this in TC39's communication hub, and was able to learn a bit more about the history behind this:

push, pop, shift, unshift were originally added to JS1.2 (Netscape 4) in 1997.

There were modeled after the similarly named functions in Perl.

JS1.2 push followed the Perl 4 convention of returning the last item pushed. In JS1.3 (Netscape 4.06 summer 1998) changed push to follow the Perl 5 conventions of returning the new length of the array.

see https://dxr.mozilla.org/classic/source/js/src/jsarray.c#804

/*
 * If JS1.2, follow Perl4 by returning the last thing pushed.  Otherwise,
 * return the new array length.
 */