How to test the availability of asm.js in a web browser?

Question

Imagine I have a asmjs script but before running the script, I'd like to test and see if the browser supports asm.js or not. If it is false, display a message indicating that the browser is old or something like that, otherwise, execute the script.

Can we utilize the idea of "use asm" somehow to detect if a web browser supports asm.js?

function MyAsmModule() {
    "use asm";
    // module body
}

Might be non doable https://github.com/kangax/compat-table/issues/447 — Yury Tarabanko, Jul 21 '17 at 15:22
Why would you want to detect that? It may run a bit slower if its not supported. — Jonas Wilms, Jul 22 '17 at 07:09
@Jonasw do you think it is going to work even if the browser doesn't support ArrayBuffer for instance? — Afshin Mehrabani, Jul 22 '17 at 07:36
No, but i think you can test if ArrayBuffers are supported... if(!"ArrayBuffer" in this) throw Error("not supported"); — Jonas Wilms, Jul 22 '17 at 07:42
By "support", do you mean being able to execute asm.js code or being able to optimize it? — Maxime, Jul 23 '17 at 13:29
@TheChetan that would work but it doesn't check the asm.js availability. — Afshin Mehrabani, Jul 24 '17 at 10:26
Perhaps you can get the browser version and compare it with this: http://caniuse.com/#feat=asmjs — TheChetan, Jul 24 '17 at 10:59
benchmark two other-wise identical functions and see if one is way faster. — dandavis, Jul 25 '17 at 21:40

score 5 · Accepted Answer · 2017-07-27T00:10:53.347

The sad situation is that there appear to be no real reliable way to detect browser support of asm.js.

Running this segment will produce an error, but not a catchable one:

try {
  (function MyAsmModule() {"use asm"})();
  console.log("asm.js OK");
  // Now, hit F12 to open the browser console just to find a TypeError that states:
  // "asm.js type error: expecting return statement"
}
catch(err) {
  // will never show...
  console.log("asm.js not supported.");
}

This is one of those cases you unwillingly have to turn to client string checking, perhaps combined with other feature checking to determine which browser and version you're dealing with.

When that information is obtained then check this list which following browsers and versions supports (courtesy of caniuse.com) asm.js, as of this date:

Version number is since and including - I included also browsers with very small user bases as the information was available for these as well:

Firefox             : v. 22
Chrome              : v. 28    (*)
Edge                : v. 13
Opera               : v. 15    (*)
Android browser     : v. 56    (*)
Opera mobile        : v. 37    (*)
Chrome for Android  : v. 59    (*)
Firefox for Android : v. 54
Samsung internet    : v.  5    (*)
QQ browser          : v.  1.2  (*)
Baidu browser       : v.  7.12 (*)

(*): "Chrome does not support Ahead-Of-Time compilation but performance doubled in Chrome 28"

How to test the availability of asm.js in a web browser?

1 Answers1