A better conversion I think.

[rdebath]

I prefer this conversion myself.

$ echo Hello World! | bf txtbf.b
[-]++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.
[-]+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.
[-]++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.
[-]++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.
[-]+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.
[-]++++++++++++++++++++++++++++++++.
[-]+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.
[-]+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.
[-]++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.
[-]++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.
[-]++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.
[-]+++++++++++++++++++++++++++++++++.
[-]++++++++++.
$ cat txtbf.b
+++++++++[>++++++++++>+++++>>+<<<<-]>+>>>+<,[<<.>.--<++.-->>[-<.>]<+++.->>.<,]
$

[jreina]

This would be beautiful but I don't even know where to start! If you have some ideas on how to do this sort of conversion, you are welcome to send a PR or just leave notes here. I mentioned in the docs that this is a naive converter but it would be an interesting exercise to do more sophisticated conversions.

[rdebath]

That conversion is still very naive; the difference being that it uses just one brainfuck tape cell to print all the characters. This cell is reset back to zero on each character with the [-] sequence.

So, as you see below I've only replaced the separator argument to join and tweaked the before and after strings.

Of course it is a little bit of a stunt to do the conversion in brainfuck, but only a little bit, after all it is a very simple conversion.

function repeat(str, times) {
  return Array(times).fill(0).map(_ => str).join('');
}

function brainfuckify(text) {
  return '[-]' + [...text]
    .map(char => char.charCodeAt(0))
    .map(asciiValue => repeat('+', asciiValue))
    .join('.\n[-]') + '.';
};

process.stdout.write(brainfuckify("Hello World!\n"));

If you're interested, a C equivalent of the BF code is a lot easier to read than the BF. I've also added some ASCII notes to save looking them up.

static unsigned char a, b, c, d, e;
static int ch;
int main(){
  c = '-';
  b = '[';
  e = '\n';
  ch = getchar(); if (ch == EOF) d = 0; else d = ch;
  while(d) {
        putchar(b);
        putchar(c);
        c -= 2; // c = '+';
        b += 2; // b = ']';
        putchar(b);
        b -= 2; // b = '[';
        while(d) {
                --d;
                putchar(c);
        }
        c += 3; // c = '.';
        putchar(c);
        --c; // c = '-';
        putchar(e);
        ch = getchar(); if (ch == EOF) d = 0; else d = ch;
  }
  return 0;
}