denormal.js

let n = 1e-320;
for (let i = 0; i < 100000; i++) {
  n = n + 1e-320;
}

n = 1e-320;
for (let i = 0; i < 100000; i++) {
  n = n - 1e-320;
}

normal.js

let n = 1e-5;
for (let i = 0; i < 100000; i++) {
  n = n + 1e-5;
}

n = 1e-5;
for (let i = 0; i < 100000; i++) {
  n = n - 1e-5;
}