Lazily flatten a nested array with generator functions

lazy_flatten.js

// Works in Chrome devtools console.
/* Yields each non-array element from a potentially nested array. */
function* lazyFlatten (element) {
    if (!Array.isArray(element))  
        yield element;  // yield non-array element
    else
        for (var element2 of element)  // unpack array into sub-elements
            for (var element3 of lazyFlatten(element2))  // flatten each sub-element...
                yield element3;  // and yield its elements
}

var nestedArray = [1, 2, [3, [4, 5]], [6, 7]];

for (var nonArray of lazyFlatten(nestedArray))
    console.log(nonArray);