[dzaima]

ECMAScript has a pretty massive amount of fully-specified behavior though; the things that differ between those implementations is nearly-entirely limited to fresh additions like `require` or whatever.

The echo thing would be like if ECMAScript allowed stuff like `"123" == 123` to give either false or true; and then indeed many things would probably break if moved across implementations.

C is the closer comparison, and indeed much software that could easily be portable (and might claim it is) often depends on implementation-specific things like 8-bit bytes, 32-bit int, assuming int8_t/etc in stdint.h exist, twos complement (before C23 at least), arithmetic shift right, etc.

[1718627440]

Because both POSIX and C are descriptive rather than prescriptive. When people have different ideas, and others already depend on both behaviour, that's the best you can do, without breaking compatibility.