@extra-array/subsequences/index.js

'use strict';
function* subsequences(x, n = -1) {
    var X = x.length;
    if (n >= X) {
        if (n === X)
            yield x;
        return;
    }
    if (n === 0 || X === 0) {
        yield [];
        return;
    }
    var y = x.slice(0, -1);
    yield* subsequences(y, n);
    for (var s of subsequences(y, n - 1)) {
        s.push(x[X - 1]);
        yield s;
    }
}
module.exports = subsequences;