Asm.js is not an alternative to JavaScript, though. It is JavaScript, just a really mangled and ugly subset of it.
cliveowen was clearly talking about "an alternative to Javascript" and "not [...] those things that eventually get translated to Javascript". Anything targeting Asm.js is merely targeting JavaScript.
The "half native speed" claim is quite dubious, at best. Even if it were realistic, that's still quite a horrible decrease in performance relative to native code. It's not as bad as the typically much worse disparity, but it's still not good at all.
Talk about JavaScript being replaced wholesale should be regarded as therapy. Therapy to dull the realisation that JavaScript is now immortal because it gained such massive reach and entrenchment. It's the web counterpart to C the immortal.
cliveowen was clearly talking about "an alternative to Javascript" and "not [...] those things that eventually get translated to Javascript". Anything targeting Asm.js is merely targeting JavaScript.
The "half native speed" claim is quite dubious, at best. Even if it were realistic, that's still quite a horrible decrease in performance relative to native code. It's not as bad as the typically much worse disparity, but it's still not good at all.