Ackermann–Péter function, with and without recursion. Faster without!

Ackermann.js

// "Canonical", recursive
const ap = (m, n) => {
  if (m === 0) return n + 1;
  if (m > 0 && n === 0) return ap(m - 1, 1);
  if (m > 0 && n > 0) return ap(m - 1, ap(m, n - 1));
};

// Non-recursive. Faster, and won't exceed call stack size!
// But maybe the array will get too huge.
const ap2 = (m, n) => {
  let cm = [];
  while (true) {
    if (m === 0) {
      if (!cm.length) return n + 1;
      m = cm.pop();
      ++n;
    } else if (m > 0 && n === 0) {
      --m;
      n = 1;
    } else if (m > 0 && n > 0) {
      --n;
      cm.push(m - 1);
    }
  }
};

// minified, golfed
a=(m,n)=>m?n?a(m-1,a(m,--n)):a(--m,1):++n
// It can go smaller:
// https://codegolf.stackexchange.com/questions/40141/the-ackermann-function


// non-recursive minified (WIP)
ax=(m,n)=>{
for(cm=[];m+cm.length;){
m?n?(cm.push(m-1),--n):n=(--m,1):m=cm.pop(++n)
}
return ++n
}

module.exports.ap = ap;
module.exports.ap2 = ap2;
module.exports.ap3 = ap3;
module.exports.a = a;
module.exports.ax = ax;