var j=0; var k=0; // before
var j=0, k=0;     // after
var j=k=0;        // better
j=k=0;            // best

function (a, b, c, d) { c = a + b; //.. } 

while (true); // usualwhile (1);    // betterfor (;;);     // best

for (i=0;i<number;i++) // usualfor (i=number;i--;)    // best

 for (i=0;i<number;i++);
 for (i=0;i<number/2;i++);

 for (i=0;i<number;i++) {
  if (i%2) {}
 }

 function(){} 012345678901

 x=function(a,b,c,d,e){ y=function(a,b,c,d,e){becomes xF,yF where F = function(a,b,c,d,e)

 setInterval(function(a,b,c,d,e){ // blabla });

 a=b;if(a){}    // before
 if(a=b){}      // after

 if (a==null) {}    // before if (!a){}          // after

 ["apple", "banana", "orange", "pineapples"] // before
 "apple0banana0orange0pineapples.split(0)    // after

 'zzzzzzzzzzzzzzzzzzzzzzzzzzzzzz' // before
 for(a="",i=30;i--;)a+='z'        // after
 a=Array(30).join('z')            // better

 Math.round(a) // before
 a+.5|0        // after 

 java -jar compiler/compiler.jar --externs externs.js --compilation_level ADVANCED_OPTIMIZATIONS --js source.js --js_output_file output.js

var a,b,c,d,e; a=10,b=....
a=10,b=.... 

 bla;bla;bla; // before bla;bla;bla  // after

 0.5 // before .5 // after

  var a = 7, b = 7, c = 7;

 ctx.arc(x, y, r, 0, 2 * Math.PI); // before
 ctx.arc(x, y, r, 0, 7);           // after