Advent of code 2019 VM

advent.js

function exec(a,b){
  let pgm = document.body.innerText.split(',').map(x=>parseInt(x));
  pgm[1] = a; pgm[2] = b;
  for(let p=0; ; p+= 4){
    if(pgm[p]==1) pgm[pgm[p+3]] = pgm[pgm[p+1]] + pgm[pgm[p+2]];
    else if(pgm[p]==2) pgm[pgm[p+3]] = pgm[pgm[p+1]] * pgm[pgm[p+2]];
    else if(pgm[p]==99) break;
    else throw new Error("invalid opcode "+pgm[p]);
  }
  return pgm[0];
}