5lines - useful utils in 5 lines or less

one.js

/* 5lines - function body must be not more than 5 SLOC */

// encrypt a string, also decrypt a string
function encrypt(key, str, s = 1) {
  // clean
  s = Number.isNaN(parseInt(s)) ? 1 : parseInt(s);
  // turn key into numbers
  key = new Uint16Array([...key].map( k => k.codePointAt(0) ));
  // write generator to produce RNG
  const rng = (function*(){while(true){yield(key.reduce((K,k,i)=>(key[(i+s)%key.length]+=k, k=(k<<1||k>>15),K+k),s),key[0])}}());  
  // encrypt string
  str = new Uint16Array( [...str].map( s => s.codePointAt(0) ) ).map( s => s ^ rng.next().value );
  // convert to characters & return
  return Array.from(str).map( s => String.fromCodePoint(s) ).join('');
}

// create a random (meant-to-be-unique) code
function rcode(s = 1) {
  s = Number.isNaN(parseInt(s)) ? 1 : parseInt(s);
  const ran32s = (crypto.getRandomValues(new Uint32Array(3)).map(v=>v^(+new Date)).map((v,i)=>v+performance.now()+i*s));
  const ran8s = new Uint8Array(ran32s.buffer);
  const ranbytes = Array.from(ran8s).map( b => String.fromCodePoint(b) );
  return btoa(ranbytes.join(''));
}