Flatten nested arrays

flatten.js

function flatten(arry) {
    var result = [];
    for (var i = 0; i < arry.length; i++) {
        if (typeof arry[i] === 'number') {
            result.push(arry[i]);
        } else {
            result = result.concat(flatten(arry[i]));
        }
    }
    return result;
}

// Test
flatten([1,2,3,[4,5,6],[7,8,9,[10,11,12], 13], 14, 15]);