delayedCallback(function(){ ... }, delay);

Hola, Amigos! it’s been a long time since I rapped at ya!

So, I’ve been doing plenty, I’m just not chatty about it. I built a Ruby migration framework using bundler, pry, spreadsheet, sequel and mp3info to build a JSON document version of my Sleepbot Environmental Broadcast database. Next up is some Node.js to serve it up, then some RequireJS, mustache & jQuery goodness to spiff up the SEB site.

But in the meanwhile, I wrote this little gem at the office:

// returns a function that will invoke the callback 'delay' ms after it is last called // eg. invoke the callback 500ms after the last time a key is pressed // based on http://stackoverflow.com/questions/2219924/idiomatic-jquery-delayed-event-only-after-a-short-pause-in-typing-e-g-timew // but fixes the following: // (a) returns a unique timer scope on every call // (b) propagates context and arguments from the last call to the returned closure // and adds .cancel() and .fire() for additional callback control // then of course, you could use underscore's _.debounce // it doesn't have the .cancel and .fire, but you may not care :) function delayedCallback(callback, delay) { return (function(callback, delay) { // (2) receives the values in scope var timer = 0; // (3a) a scoped timer var context, args; // (3b) scoped copies from the last invocation of the returned closure var cb = function() { callback.apply(context, args); } // (3c) called with proper context + arguments var dcb = function() { // (4) this closure is what gets returned from .delayedCallback context = this; args = arguments; window.clearTimeout(timer); timer = window.setTimeout(cb, delay); // (5) only fires after this many ms of not re-invoking }; dcb.cancel = function() { window.clearTimeout(timer); }; // (6a) you can cancel the delayed firing dcb.fire = function() { this.cancel(); cb(); }; // (6b) or force it to fire immediately return dcb; })(callback, delay); // (1) capture these values in scope }

Yes, I know. So it turns out that I didn’t know about underscore’s _.debounce() when I wrote it. Eh. So much for DRY ¯\(ツ)/¯

Still – I’m glad I thought it through. It exercises all the best features of JavaScript / ECMAScript:

scope-capturing closures
specifiable function context
freestyle properties on Object instances
single-threading (look ma, no Mutex! no synchronize { ... } !)

Anyway. Bla dee blah. This post also gave me the incentive to start embedding gists in my blog. Nice helper widget, dflydev !

Peace out.

NOTE: If your screen reader is reading this, please contact me at admin@cantremember.com ... because it shouldn't. FIXME: build this dynamically based upon the maximum content in any sub-Element of this Element. I will call this my "Safari Reader Counterweight". In some of my Posts, I have huge code excerpts, etc. Safari Reader, at least in iOS, will identify the 'main Element', the one it features, based upon its content length. Sometimes those code excerpts get identified as the 'main Element', and the Post is borked in Safari Reader mode. This is a counter-weight; it gives the <main> Element additional content so that it gets featured, algorithmically. Yes, it increases the payload of every page (@see FIXME above). But not by that much. Then again, this is a guess as to how much content any given Element could contain. If it's not enough, BOOM, Safari Reader looks like crap. So, here's a great article on how to enable Safari Reader on your site. It's mostly guesswork, but those guesses helped me debug this obtuse goddamn problem. Oh, and look, you can enter and exit Reader programmatically. JavaScript can fix anything. I promise I will never cut-and-paste lines of text simply to add Element payload. I promise I will never cut-and-paste lines of text simply to add Element payload. I promise I will never cut-and-paste lines of text simply to add Element payload. I promise I will never cut-and-paste lines of text simply to add Element payload. I promise I will never cut-and-paste lines of text simply to add Element payload. I promise I will never cut-and-paste lines of text simply to add Element payload. I promise I will never cut-and-paste lines of text simply to add Element payload. I promise I will never cut-and-paste lines of text simply to add Element payload. I promise I will never cut-and-paste lines of text simply to add Element payload. I promise I will never cut-and-paste lines of text simply to add Element payload. I promise I will never cut-and-paste lines of text simply to add Element payload. I promise I will never cut-and-paste lines of text simply to add Element payload. I promise I will never cut-and-paste lines of text simply to add Element payload. I promise I will never cut-and-paste lines of text simply to add Element payload. I promise I will never cut-and-paste lines of text simply to add Element payload. I promise I will never cut-and-paste lines of text simply to add Element payload. I promise I will never cut-and-paste lines of text simply to add Element payload. I promise I will never cut-and-paste lines of text simply to add Element payload. I promise I will never cut-and-paste lines of text simply to add Element payload. I promise I will never cut-and-paste lines of text simply to add Element payload. I promise I will never cut-and-paste lines of text simply to add Element payload. I promise I will never cut-and-paste lines of text simply to add Element payload. I promise I will never cut-and-paste lines of text simply to add Element payload. I promise I will never cut-and-paste lines of text simply to add Element payload.