Function lengthen

docs/app/js/sanddance-app.js:141222–141227

(array2, length, copy)

    };
}
function lengthen(array2, length, copy) {
    if (array2.length >= length) return array2;
    copy = copy || new array2.constructor(length);
    copy.set(array2);
    return copy;
}
function array(n, m, array3) {
    const copy = (m < 0x101 ? array8 : m < 0x10001 ? array16 : array32)(n);
    if (array3) copy.set(array3);