use typedarray, about 15% faster

lib/b64.js

@@ -3,6 +3,10 @@
 
   var lookup = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';
 
+  function decode (c) {
+    return indexOf(lookup, c)
+  }
+
   function b64ToByteArray(b64) {
     var i, j, l, tmp, placeHolders, arr;
   
@@ -19,25 +23,31 @@
     placeHolders = placeHolders > 0 ? b64.length - placeHolders : 0;
 
     // base64 is 4/3 + up to two characters of the original data
-		arr = [];//new Uint8Array(b64.length * 3 / 4 - placeHolders);
+    arr = new Uint8Array(b64.length * 3 / 4 - placeHolders);
 
     // if there are placeholders, only get up to the last complete 4 chars
     l = placeHolders > 0 ? b64.length - 4 : b64.length;
 
+    var L = 0
+
+    function push (v) {
+      arr[L++] = v
+    }
+
     for (i = 0, j = 0; i < l; i += 4, j += 3) {
-			tmp = (indexOf(lookup, b64.charAt(i)) << 18) | (indexOf(lookup, b64.charAt(i + 1)) << 12) | (indexOf(lookup, b64.charAt(i + 2)) << 6) | indexOf(lookup, b64.charAt(i + 3));
-			arr.push((tmp & 0xFF0000) >> 16);
-			arr.push((tmp & 0xFF00) >> 8);
-			arr.push(tmp & 0xFF);
+      tmp = (decode(b64.charAt(i)) << 18) | (indexOf(lookup, b64.charAt(i + 1)) << 12) | (decode(b64.charAt(i + 2)) << 6) | decode(b64.charAt(i + 3));
+      push((tmp & 0xFF0000) >> 16);
+      push((tmp & 0xFF00) >> 8);
+      push(tmp & 0xFF);
     }
 
     if (placeHolders === 2) {
-			tmp = (indexOf(lookup, b64.charAt(i)) << 2) | (indexOf(lookup, b64.charAt(i + 1)) >> 4);
-			arr.push(tmp & 0xFF);
+      tmp = (decode(b64.charAt(i)) << 2) | (decode(b64.charAt(i + 1)) >> 4);
+      push(tmp & 0xFF);
     } else if (placeHolders === 1) {
       tmp = (indexOf(lookup, b64.charAt(i)) << 10) | (indexOf(lookup, b64.charAt(i + 1)) << 4) | (indexOf(lookup, b64.charAt(i + 2)) >> 2);
-			arr.push((tmp >> 8) & 0xFF);
-			arr.push(tmp & 0xFF);
+      push((tmp >> 8) & 0xFF);
+      push(tmp & 0xFF);
     }
 
     return arr;