JSON, XML performance | Hacker News Reader

JSON, XML performance

labs.mudynamics.com

15 pointskowsik7 comments

In my experience, that which kills "snappyness" for commercial sites is primary annoyingly slow industry standard ad- and traffic-tracking-systems, and secondary layout rendering issues due to complex css or silly number of images.

(Lesson learned: make sure you can serve pages without ad and tracking scripts to show the customer that you are fast as hell, that it is their "money-maker dependencies" that kill snappiness)

Javascript can often be hidden behind some user-initiated click, where it "feels" okay to have 1 or 2 sec of delay given that some feedback is given directly, such as changing the mouse pointer or the color of the button pressed.

I wish github would let me be the initiator of more of their page updates, because those pages can be really slow to finish using my weaker machines.

Could you specify which parts of GitHub you're referring to? We're always looking for way to improve the site.

Umm... Am I missing something? The blog post describes comparing XML parsing to JSON parsing, but that chart compares JSON parse time to XHR request time for that JSON file!

The real chart he should be referring to is here: http://ejohn.org/apps/jsonvxml2/json-speeds.png

actually, this one's better:

http://ejohn.org/apps/jsonvxml/jsonvxml.png

I think the scenario described in the post might be deliberately contrived. JQuery uses window.eval ( http://dev.jquery.com/browser/trunk/jquery/src/ajax.js#L503 ) to parse JSON, not Douglas Crockford's json.js. So, merely swapping XML with JSON shouldn't result in as much of a slow down (if not a speedup) as the graph tends to indicate.

http://www.json.org/json2.js

and here's the appropriate comment:

  // In the third stage we use the eval function to compile the text into a
  // JavaScript structure. The '{' operator is subject to a syntactic ambiguity
  // in JavaScript: it can begin a block or an object literal. We wrap the text
  // in parens to eliminate the ambiguity.

So um, json.js does use eval, same as jQuery.

On http://www.pcapr.net, we use tons of javascript and I've noticed returning "large" JSON arrays makes quite a few different browsers croak.