fatten

flatten.js

var flatten = function (v, cb, result) {
	result = result || [];
	
	if (v instanceof Array) {
		v.forEach(function (v) { flatten(v, cb, result); });
		return result
	}
	result.push(cb ? cb(v) : v);
	return result;
};

console.log(flatten([
	"a",
	[
        "b", 
        "c", [
            "d"
        ]
    ]
]));