timestamp_to_snowflake.js

let epoch = 1420070400000;
let increment = 0;

function timestamp_to_snowflake (timestamp = Date.now()) {
  let snowflake = '';

  // timestamp
  snowflake += (timestamp - epoch).toString(2).padStart(42, '0');
  // worker id
  snowflake += '00001';
  // process id
  snowflake += '00000';
  // increment
  snowflake += (increment++ % 2**12).toString(2).padStart(12, '0');

  return BigInt('0b' + snowflake);
}