Space and time of local variable vs. this

[espruino-discuss]

Posted at 2016-08-18 by @allObjects

@gordon, what's your implementation-knowing 'guess'? ...space / memory footprint, time / performance?

var obj =
{ property:123
, funWithThis: function() {
    // function/method using 'this' in body
    // lots of lots this.something(); this.somethingThat(); ...
    return this.property;
  }
, funWithLocalVariable: function() {
    // function/method using 'var _ that references this' in body
    var _ = this;
    // lots of lots _.something(); _.somethingThat(); ...
  }
  return _;
};

[gfwilliams]

Posted at 2016-08-18 by @gfwilliams

You'd have to do some tests...

It'd be close...

• this is a reserved word, so accesses will be faster as there's no lookup.
• But _ is short, and a local variable, so parsing will be faster and lookups shouldn't be that slow either.

But funWithLocalVariable would probably minify much better.

[espruino-discuss]

Posted at 2016-08-18 by @allObjects

Thanks. ...somewhat as expected. Here two methods of a singleton that use local _-reference for this.:

...
, d: function(e) { var _=this; ((e)?[e]:_.es).forEach(function(e){
   _[e[1]+"D"].apply(_,e); }); return _; }
, clr: function(cx,i) { var _=this, c; if (cx<0) {
    c=_.clrs[0].apply(_,_.clrs[-cx]); 
  } else { c=cx^((i)?7:0); c=[(c&4)>>2,(c&2)>>1,c&1]; }
  _.lcd.setColor.apply(_.lcd,c); return _; }
...

...that's why I like 'older' virtual/late-late-binding/interpreted languages that use ^ for noisy return... ;-) ...and old new things for the dredging function: => ...and function / block w/ arguments definition: [ :a :b | ...code using local vars a, b ]. ...some 'good old times' that did not need the curly braces and parenthesis salad...