IndexOf is Javascript 1.6, IN is 1.4

Given that IN is implemented on 1.4 and IE8 friendly (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/in VS https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/indexOf), seems like it is even more performant.
This is a benchmark test I executed:

var Bench = require('bench');
var Stringify = require('./json-stringify-safe');
var StringifyIN = require('./stringify');

var list = [];
for (var i = 0; i < 1000; ++i ) { // tried 100, 1000, 10000
    list.push({'some' : 'thing' + i}); // tried 'some': 'thing' as well, but I wanted to test multiple values
}

exports.compare = {
    'safe stringify' : function () {

        return Stringify(list);
    },
    'safe stringify IN' : function () {

        return StringifyIN(list);
    }
};
Bench.runMain();

This is what happens:


Please be patient.
{ http_parser: '1.0',
  node: '0.8.3',
  v8: '3.11.10.15',
  ares: '1.7.5-DEV',
  uv: '0.8',
  zlib: '1.2.3',
  openssl: '1.0.0f' }
Scores: (bigger is better)

safe stringify IN
Raw:
 > 0.8130081300813008
 > 0.8097165991902834
 > 0.78064012490242
 > 0.8110300081103001
Average (mean) 0.8035987155710761

safe stringify
Raw:
 > 0.21299254526091588
 > 0.2114611968703743
 > 0.21272069772388855
 > 0.21249468763280918
Average (mean) 0.212417281871997

Winner: safe stringify IN
Compared with next highest (safe stringify), it's:
73.57% faster
3.78 times as fast
0.58 order(s) of magnitude faster
QUITE A BIT FASTER