NodeJS script to generate FF script to keep in the font required characters only

ff_unique_symbols.js

/*
USAGE:

1. RUN:
node ff_unique_symbols.js

2. Copy the result, i.e. the FF script.
3. Open a font in FontForge
4. File -> Execute Script
5. In the popup select FF, paste the script.
6. Execute it.
7. Save the font.

*/

function onlyUnique(value, index, self) {
    return self.indexOf(value) === index;
}

function escapeChar(escape) {
    return '"u' + ("0000" + escape.charCodeAt().toString(16)).slice(-4) + '"';
}

// --> INSERT HERE REQUIRED CHARACTERS OR JUST ALL STRINGS FROM YOUR GAME
const text = " 0123456789~-+";
// ^^^ (it's a nice idea to keep the characters " " (space) and "~" (tilde))

// Keep only unique characters
let chars = text.split("").filter(onlyUnique).map(escapeChar);

// Output the FF scripts
console.log("SelectNone()");
while (chars.length > 0) {
    console.log("SelectMore(" + chars.splice(0, 1).join(", ") + ")");
}
console.log("SelectInvert()");
console.log("DetachAndRemoveGlyphs()");
console.log("Reencode(\"compacted\")");

Online tool - https://jsbin.com/molahek