0-conditional-iteration.js

var callbacks = Array.prototype.forEach.call(
    "abcdefg",
    function (letter) {
        // or some expensive computation
        return letter;
    }
);

return callbacks.reduceRight(function (otherwise, callback) {
    var letter = callback();
    if (letter === "h") {
        return letter;
    } else {
        return otherwise();
    }
}, function () {
    throw new Error("Can't find H");
});

1-flow.txt

A->B->C->D->E->F->G->otherwise
|  |  |  |  |  |  |
v  v  v  v  v  v  v
a  b  c  d  e  f  g

This was linked from the Q library examples. I'm not really sure how this solves the problem of breaking out of a promise chain. Can you explain?