Much faster implementation

index.browser.js

@@ -1,6 +1,6 @@
 // This file replaces `index.js` in bundlers like webpack or Rollup,
 // according to `browser` config in `package.json`.
-
+import { urlAlphabet } from './url-alphabet/index.js';
 export { urlAlphabet } from './url-alphabet/index.js'
 
 export let random = bytes => crypto.getRandomValues(new Uint8Array(bytes))
@@ -47,25 +47,12 @@ export let customRandom = (alphabet, defaultSize, getRandom) => {
 export let customAlphabet = (alphabet, size = 21) =>
   customRandom(alphabet, size, random)
 
-export let nanoid = (size = 21) =>
-  crypto.getRandomValues(new Uint8Array(size)).reduce((id, byte) => {
-    // It is incorrect to use bytes exceeding the alphabet size.
-    // The following mask reduces the random byte in the 0-255 value
-    // range to the 0-63 value range. Therefore, adding hacks, such
-    // as empty string fallback or magic numbers, is unneccessary because
-    // the bitmask trims bytes down to the alphabet size.
-    byte &= 63
-    if (byte < 36) {
-      // `0-9a-z`
-      id += byte.toString(36)
-    } else if (byte < 62) {
-      // `A-Z`
-      id += (byte - 26).toString(36).toUpperCase()
-    } else if (byte > 62) {
-      id += '-'
-    } else {
-      id += '_'
-    }
-    return id
-  }, '')
-
+export let nanoid = (len = 21) => {
+  let id = "";
+  let rand = crypto.getRandomValues(new Uint8Array(len));
+  // Using the bitwise AND operator to "cap" the value of
+  // the random byte from 255 to 63, in that way we can make sure
+  // that the value will be a valid index for the "chars" string.
+  for (let i = 0; i < len; i++) id += urlAlphabet[rand[i] & 63];
+  return id;
+}

package.json

@@ -79,7 +79,7 @@
     {
       "name": "nanoid",
       "import": "{ nanoid }",
-      "limit": "109 B"
+      "limit": "124 B"
     },
     {
       "name": "customAlphabet",