You can save execution time by assigning values to variables at the same time there are initilized.

var myString;
var myArray;
 
myString = 'lorem ';
myString += 'ipsum';
 
myArray = new Array();
myArray.push('foo');
myArray.push('bar');

You can also save a little amount of time by avoiding concating strings via the += operator.

var myString = 'lorem ipsum';
var myArray = ['foo', 'bar'];