Why does sqrt(x+1)-sqrt(x) result to 0 in JS? [duplicate]

I’m trying to compute the difference between two square roots in JS.

function diffSqrt(x) {
  return Math.sqrt(x + 1) - Math.sqrt(x);
}

console.log(deltaSqrt(1e6));   // 0.0004999998750463419
console.log(deltaSqrt(1e12));  // 5.00003807246685e-07
console.log(deltaSqrt(1e16));  // 0.0

Why does it go all the way to 0.0 for a larger x?

I just wrote the straightforward implementation subtracting two square roots. I expected something small but non-zero like 5e-11.