All binary srings of given length

binary_strings.js

#!/usr/bin/env node

function memoize(fn) {
  const cache = {};
  return (...args) => {
    const key = JSON.stringify(args);
    cache[key] = cache[key] || fn(...args);
    return cache[key];
  };
}

let binaryStrings = memoize(function (level) {
  if (level < 0) {
    throw new Error("Expected a nonnegative integer");
  }

  const bits = ["0", "1"];
  const result = [];

  if (level === 0) {
    return result;
  }

  if (level === 1) {
    return bits;
  }

  for (const string of binaryStrings(level - 1)) {
    for (const bit of bits) {
      result.push(bit + string);
    }
  }

  return result;
});

function main(level = 0) {
  console.log(`-- Binary strings of length ${level}`);
  for (const string of binaryStrings(Number(level))) {
    console.log(string);
  }
}

main(...process.argv.slice(2));