diff --git a/lib/b64.js b/lib/b64.js
index b27872c..3a4666c 100644
--- a/lib/b64.js
+++ b/lib/b64.js
@@ -15,7 +15,7 @@
 		// represent one byte
 		// if there is only one, then the three characters before it represent 2 bytes
 		// this is just a cheap hack to not do indexOf twice
-		placeHolders = b64.indexOf('=');
+		placeHolders = indexOf(b64, '=');
 		placeHolders = placeHolders > 0 ? b64.length - placeHolders : 0;
 
 		// base64 is 4/3 + up to two characters of the original data
@@ -25,17 +25,17 @@
 		l = placeHolders > 0 ? b64.length - 4 : b64.length;
 
 		for (i = 0, j = 0; i < l; i += 4, j += 3) {
-			tmp = (lookup.indexOf(b64[i]) << 18) | (lookup.indexOf(b64[i + 1]) << 12) | (lookup.indexOf(b64[i + 2]) << 6) | lookup.indexOf(b64[i + 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);
 		}
 
 		if (placeHolders === 2) {
-			tmp = (lookup.indexOf(b64[i]) << 2) | (lookup.indexOf(b64[i + 1]) >> 4);
+			tmp = (indexOf(lookup, b64.charAt(i)) << 2) | (indexOf(lookup, b64.charAt(i + 1)) >> 4);
 			arr.push(tmp & 0xFF);
 		} else if (placeHolders === 1) {
-			tmp = (lookup.indexOf(b64[i]) << 10) | (lookup.indexOf(b64[i + 1]) << 4) | (lookup.indexOf(b64[i + 2]) >> 2);
+			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);
 		}
@@ -50,7 +50,7 @@
 			temp, length;
 
 		function tripletToBase64 (num) {
-			return lookup[num >> 18 & 0x3F] + lookup[num >> 12 & 0x3F] + lookup[num >> 6 & 0x3F] + lookup[num & 0x3F];
+			return lookup.charAt(num >> 18 & 0x3F) + lookup.charAt(num >> 12 & 0x3F) + lookup.charAt(num >> 6 & 0x3F) + lookup.charAt(num & 0x3F);
 		};
 
 		// go through the array every three bytes, we'll deal with trailing stuff later
@@ -63,15 +63,15 @@
 		switch (extraBytes) {
 			case 1:
 				temp = uint8[uint8.length - 1];
-				output += lookup[temp >> 2];
-				output += lookup[(temp << 4) & 0x3F];
+				output += lookup.charAt(temp >> 2);
+				output += lookup.charAt((temp << 4) & 0x3F);
 				output += '==';
 				break;
 			case 2:
 				temp = (uint8[uint8.length - 2] << 8) + (uint8[uint8.length - 1]);
-				output += lookup[temp >> 10];
-				output += lookup[(temp >> 4) & 0x3F];
-				output += lookup[(temp << 2) & 0x3F];
+				output += lookup.charAt(temp >> 10);
+				output += lookup.charAt((temp >> 4) & 0x3F);
+				output += lookup.charAt((temp << 2) & 0x3F);
 				output += '=';
 				break;
 		}
@@ -82,3 +82,22 @@
 	module.exports.toByteArray = b64ToByteArray;
 	module.exports.fromByteArray = uint8ToBase64;
 }());
+
+function indexOf (arr, elt /*, from*/) {
+	var len = arr.length;
+
+	var from = Number(arguments[1]) || 0;
+	from = (from < 0)
+		? Math.ceil(from)
+		: Math.floor(from);
+	if (from < 0)
+		from += len;
+
+	for (; from < len; from++) {
+		if ((typeof arr === 'string' && arr.charAt(from) === elt) ||
+				(typeof arr !== 'string' && arr[from] === elt)) {
+			return from;
+		}
+	}
+	return -1;
+}
diff --git a/test/runner.js b/test/runner.js
index 8f65b53..33d6697 100644
--- a/test/runner.js
+++ b/test/runner.js
@@ -15,15 +15,15 @@
 		],
 		res;
 
-	res = checks.some(function (check) {
+	res = some(checks, function (check) {
 		var b64Str,
 			arr,
 			str;
 
-		b64Str = b64.fromByteArray(Array.prototype.map.call(check, function (char) { return char.charCodeAt(0); }));
+		b64Str = b64.fromByteArray(map(check, function (char) { return char.charCodeAt(0); }));
 
 		arr = b64.toByteArray(b64Str);
-		str = arr.map(function (byte) { return String.fromCharCode(byte); }).join('');
+		str = map(arr, function (byte) { return String.fromCharCode(byte); }).join('');
 		if (check !== str) {
 			console.log('Fail:', check);
 			console.log('Base64:', b64Str);
@@ -37,3 +37,28 @@
 		console.log('All tests passed!');
 	}
 }());
+
+function some (arr, fun) {
+	for (var i = 0, len = arr.length; i < len; i++) {
+		if (i in arr && fun(arr[i], i, arr)) {
+			return true;
+		}
+	}
+	return false;
+}
+
+function map (arr, callback) {
+	var res = [];
+	for (var k = 0, len = arr.length; k < len; k++) {
+		if ((typeof arr === 'string' && !!arr.charAt(k))) {
+			var kValue = arr.charAt(k);
+			var mappedValue = callback(kValue, k, arr);
+			res[k] = mappedValue;
+		} else if (typeof arr !== 'string' && k in arr) {
+			var kValue = arr[k];
+			var mappedValue = callback(kValue, k, arr);
+			res[k] = mappedValue;
+		}
+	}
+	return res;
+}
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