self.onMessage = function(event) {
    event.data.push('five');
    console.log(event.data.join(' '));
    self.postMessage();
};

var numbers = [ 'one', 'two', 'three' ];
var worker = new Worker('myWorker.js');
worker.onMessage = function(event) {
    console.log(numbers.join(' '));
};
worker.postMessage(numbers);
numbers.push('four');

one two three five
one two three four
// Objects posted between threads are copied,
// not passed by reference