Using JavaScript to fill localStorage to its maximum capacity

fill-localstorage.ts

/**
 * Fill localStorage to its maximum capacity.
 *
 * First, we find the highest order bit (the bit with the highest place value)
 * that fits in localStorage by storing localStorage an increasingly big
 * string of length 2, 4, 8, 16, etc. until it won't fill localStorage anymore.
 *
 * By working in iterations, starting with very long strings, and storing data
 * in different items, we can keep a low memory profile and reduce the number of
 * writes — making this process pretty fast.
 *
 * To cleanup localStorage you can use localStorage.clear(). Still, just in case
 * you wanted to clean up only the data stored by this function (maybe because
 * you want to keep in the localStorage the stuff you stored before running it),
 * we return a convenient cleanup function.
 *
 * @return A cleanup function to delete the data we stored.
 */
function fillLocalStorage(): () => void {
  const key = "__filling_localstorage__";

  let max = 1; // This holds the highest order bit.
  let data = "x"; // The string we're going to store in localStorage.

  // Find the highest order bit by storing in localStorage an increasingly big
  // string of length 2, 4, 8, 16, etc. (basically doubling its size and always
  // follow a power of two) until it doesn't fill localStorage anymore.
  try {
    while (true) {
      data = data + data;
      localStorage.setItem(key, data);
      max <<= 1;
    }
  } catch {}

  // Then again, fill the rest of the space by increasing the string length
  // in the opposite order of the one used above.
  for (let bit = max >> 1; bit > 0; bit >>= 1) {
    try {
      localStorage.setItem(key, data.substring(0, max | bit));
      max |= bit;
    } catch {
      // Storage is now completely full 🍟
    }
  }

  // Cleanup
  return function cleanup() {
    localStorage.removeItem(key);
  };
}

Snippet extracted from "Using JavaScript to fill localStorage to its maximum capacity"