John-David Dalton - Perf the web forward

JSConf US 2013

31 May 2013

Talking about how to improve existing libraries and your own code with some performance gains techniques. John-David is the creator of


optimize for the common case use natives wisely - array foreach, filter, map, etc vs for loops etc as alternatives avoid abstraction - reduce function calls, etc balance pros/cons

Hoist call & apply

(dojo, ember, jquery, prime, underscore would all benefit) from: while loop { } to: callback = createCallback() < - do this outside the loop, createCallback returns then do callback(values) within loop

Avoid binding

By detecting “this” use if not using this, don’t bind

Reduce searches

indexOf is searching through entire array, large arrays therefore slower if test on property (obj[key] exists?) that’s better but integer 2 == string “2” so unique operations will fail cache parts of large arrays in to smaller arrays for searching (applies to underscore, possibly jquery - these would benefit)

Coerce with care

arguments - don’t need to slice, can apply it instead of underscore’s flatten (or homegrown) you can concat (native) - use Array.prototype as the this argument no need to create new

array.push can accept more than one argument

Sugar in moderation

chaining API has performance cost in some libs, generic api in others - be aware of fast/slow paths

lazy.js - very performant in chaining

twitter: @jdalton


www: (underscore alternative)


hashtag for this talk: #perffwd

JSConf 2013

This is a quick summary of a talk I attended at JSConf 2013. You can see a list of all those I've summarized notes from here. There's also a General thoughts during JSConf 2013 post for all the non-talk bits and pieces.

There were 3 concurrent tracks at the conference, so only those I attended myself are summarized here. Other attendees have summarized some of the talks I didn't get to due to scheduling conflicts - you can find those at (James Long) and Toby Ho's github repo.