Find unique non-ASCII characters in a UTF-8 file

utfanal.js

let fs = require("fs"); 
let myArgs = process.argv.slice(2);

fs.readFile(myArgs[0], "utf8", function (err, data) {
  if (err) throw err;
  const ar = Array.from(data);
  let table = [];
  ar.forEach(function(k) {
    if (k.codePointAt(0) > 127 && table.indexOf(k)<0) {
      let bn = encodeURIComponent(k).replace(/%[A-F\d]{2}/g, 'U').length;
      console.log(`\u001b[97;1m${k}\u001b[0m \u001b[${bn==2?'32':bn==3?'33':'31'}m(${bn} bytes)\u001b[0m`);
      table.push(k);
    }
  });
  
  console.log(table.join(' '));  
  console.log(`\u001b[97m${table.length} slots in look-up table required.\u001b[0m`);
});