This contains methods for setting up an [link:https://developer.mozilla.org/en-US/docs/Web/API/AudioContext AudioContext].
Used internally by the [page:AudioListener AudioListener] and [page:AudioLoader AudioLoader] classes.
This uses the [link:https://developer.mozilla.org/en-US/docs/Web/API/Web_Audio_API Web Audio API].
Return the value of the variable `context` in the outer scope, if defined, otherwise set it to a new [link:https://developer.mozilla.org/en-US/docs/Web/API/AudioContext AudioContext].
Set the variable `context` in the outer scope to `value`.
[link:https://github.com/mrdoob/three.js/blob/master/src/[path].js src/[path].js]