function* in JavaScript

In this page I found a new JavaScript function type:

// NOTE: "function*" is not supported yet in Firefox.

// Remove the asterisk in order for this code to work in Firefox 13 



function* fibonacci() { // !!! this is the interesting line !!!

    let [prev, curr] = [0, 1];

    for (;;) {

        [prev, curr] = [curr, prev + curr];

        yield curr;

    }

}