Google Closure JavaScript compiler optimization examples.

optexamples.js

// a statement like this...
if (fruit == 'apples') fruit = 'bananas';

// is converted to this...
'apples'==fruit&&(fruit='bananas');


// next... a statement like this...
if (fruit !== undefined) callMe();

// is converted to this...
if(void 0!==fruit)callMe();


// truthy values
var myVariable = true;

// are converted to this...
myVariable=!0;


// pre-calculated math
var COOKIE_LIFETIME_DAYS = 30,
	expireUTC = new Date();

	// calculate expiry time for cookie
	expireUTC.setTime(
		expireUTC.getTime() +
		(COOKIE_LIFETIME_DAYS * 24 * 60 * 60 * 1000) // hours * minutes * seconds * microseconds
	);

// is converted to this
var b=new Date;b.setTime(b.getTime()+2592E6);