Q:

JavaScript array iteration direction

When processing a very large in-memory array of uniform (same-type) JavaScript objects (each with just a few columns)...
Is there any impact on performance and/or or any other penalty to consider when choosing to iterate through it as row->column versus column->row?
Example
We have 100,000 data rows from a CSV file, each is an object with 10 integer values, and we need to touch every value in it for a certain calculation.
Will it make any difference whether we iterate through it vertically or horizontally? Does the modern V8 care about such things in the slightest?
var data = [...]; // array of many same-type objects;

// horizontal iteration:
for (var p in data[0]) {
    for (var i = 0; i < data.length; i++) {
        var value = data[i][p]; // current value;
        // calculate here from the value;
    }
}

// vertical iteration:
for (var i = 0; i < data.length; i++) {
    for (var p in data[0]) {
        var value = data[i][p]; // current value;
        // calculate here from the value;
    }
}

A:

Only one way to be sure is to run some benchmarks, I made a jsperf: http://jsperf.com/vertical-vs-horizontal-loop The results depends on the engine like expected. Early results from tests I did (Chrome 42 is Edge on Window 10): 
|     UserAgent    | horizontal iteration | vertical iteration | vertical iteration with caching | # Tests |
|:----------------:|:--------------------:|:------------------:|:-------------------------------:|:-------:|
| Chrome 42.0.2311 |         1,067        |         287        |               226               |    2    |
|   Firefox 43.0   |         5,621        |         415        |               443               |    2    |
|      IE 11.0     |          976         |         441        |               313               |    2    |
|  Iron 46.0.2450  |         1,557        |         901        |              1,907              |    2    |
(numbers are ops/s, the higher the better)

Interestingly enough, horizontal iteration ranges from twice faster to dozen of times faster (on Firefox). But vertical iteration with caching is the fastest only on Iron 46 (Chromium fork so V8 engine).
Benchmarks with node v5.1.0:

horizontal iteration x 1,140 ops/sec ±1.11% (63 runs sampled)
  vertical iteration x 833 ops/sec ±0.92% (68 runs sampled)
  vertical iteration with caching x 1,678 ops/sec ±1.13% (67 runs sampled)
  Fastest is vertical iteration with caching

