Linux-like permission thing

index.js

function parseNumericPerms (s) {
  var operm = parseInt(s,8); // octal
  function i (a) {
    return Boolean(operm&(2**(a-1)));
  }
  return {
    o: {r:i(3),w:i(2),x:i(1)},
    g: {r:i(6),w:i(5),x:i(4)},
    u: {r:i(9),w:i(8),x:i(7)}
  }
}
function toStr (t) {
  var u = t.u;
  var g = t.g;
  var o = t.o;
  var arr = [
    u.r,u.w,u.x,
    g.r,g.w,g.x,
    o.r,o.w,o.x
  ];
  return arr.map((a,b)=>{return a?"rwx"[b%3]:"-"}).join("");
}
function perm(t,type,level){
  return t[type][level];
}
var groups = {};
function addGroup(g,u) {
  if(!groups[g]) groups[g]=[];
  groups[g].push(u);
}
function remFromGroup(g,u){
  var pos = groups[g].indexOf(u);
  if(pos==-1) return;
  groups.g.splice(pos,1);
}
function remGroup(g){
  delete groups[g];
}
function newObject(perm,owner,gowner) {
  var obj = {};
  obj.p = parseNumericPerms(perm);
  obj.o = owner;
  obj.g = gowner;
  obj.perms = function(u) {
    var ug = !!~(groups[obj.g]||[]).indexOf(u);
    var uu = obj.o == u;
    let r = obj.p.o.r||(obj.p.g.r&&ug)||(obj.p.u.r&&uu);
    let w = obj.p.o.w||(obj.p.g.w&&ug)||(obj.p.u.w&&uu);
    let x = obj.p.o.x||(obj.p.g.x&&ug)||(obj.p.u.x&&uu);
    return {r,w,x}
  }
  return obj;
}
/*
addGroup("asdf","test");
var o = newObject(721,"cows","asdf");
console.log(o.perms("hi")) // x
console.log(o.perms("test")) // wx
console.log(o.perms("cows")) // rwx
*/