Using Buffer.from instead of constructor form.

Author: andrewplummer

lib/string.js

@@ -377,10 +377,10 @@ function buildBase64() {
   // istanbul ignore if
   if (typeof Buffer !== 'undefined') {
     encodeBase64 = function(str) {
-      return new Buffer(str).toString('base64');
+      return Buffer.from(str).toString('base64');
     };
     decodeBase64 = function(str) {
-      return new Buffer(str, 'base64').toString('utf8');
+      return Buffer.from(str, 'base64').toString('utf8');
     };
     return;
   }