javascript - Unclear about V8 Garbage Collection -

i having hard time wrapping head around garbage collected in node.js v8 , why (or why not). have example below using async.js library.

i love insight how v8 treats each case below (numbered 1 6 in comments).

thanks in advance.

"use strict";  var async = require('async');  module.exports = {      foo: function foo(shirt, callback) {          async.series([              function(next) {                  var pants = 'clown',                     outfit = shirt + pants;                  // 1. shirt garbage collected?                  next(null, outfit);              },              function(next) {                  var err = new error('can\'t touch this.'),                     pants = 'hammer',                     outfit = shirt + pants;                  // 2. shirt garbage collected?                  setimmediate(function() {                      // 3. err garbage collected?                     // 4. outfit garbage collected?                     // 5. next garbage collected?                      next(err, outfit);                  })              }          ], function(err, results) {              // 6. callback garbage collected?             callback(err, results);          });      }   }; 

both shirt (1, 2) , callback (3) referenced inner functions. bindings have heap-allocated, , become garbage when inner functions have become garbage. in example, happen after async.series has finished execution , dropped reference array in inner functions stored.

of course, both shirt , callback parameters. when foo drops references values, caller still have some, in case these values stay alive longer. cannot know locally.

similarly, err (3) , outfit (4) become garbage when inner function passed setimmediate, references them, becomes garbage (which happen after executed), , when whatever continuation next passes them not keep them alive longer. in example, passed on callback parameter don't know -- keep them alive indefinitely storing them away somewhere, or drop them immediately.

finally, next (5) argument again. value live @ least until setimmediate fires. function async.series creates, , know how long lives you'd know in detail how async.series handles (i assume drops immediately).