How to detect HTML5 audio MP3 support?

var test_audio= document.createElement("audio") //try and create sample audio element 
var test_video= document.createElement("video") //try and create sample video element
var mediasupport={audio: (test_audio.play)? true : false, video: (test_video.play)? true :     false}

alert("Audio Element support: " + mediasupport.audio + "\n"
+ "Video Element support: " + mediasupport.video
)

You could either check the User-Agent and see what browser is being used or you could test support with Javascript.

var a = document.createElement('audio');
return !!(a.canPlayType && a.canPlayType('audio/mpeg;').replace(/no/, ''));

I got the above code from this page.

return !!(a.canPlayType) is better because (some recent versions of)Firefox not supports mp3 and a.canPlayType('audio/mpeg;') will be false

Modernizr is a library for feature detection. You can use it to do the work for you.

According to the documentation:

If audio support is detected, Modernizr assesses which formats the current browser will play. Currently, Modernizr tests ogg, mp3, wav and m4a.

Important: The values of these properties are not true booleans. Instead, Modernizr matches the HTML5 spec in returning a string representing the browser's level of confidence that it can handle that codec. These return values are an empty string (negative response), "maybe" and "probably". The empty string is falsy, in other words: Modernizr.audio.ogg == '' and '' == false