Use string concatenation to build the output string

Switching from pushing to an array and using .join() to using simple string concatenation yields performance gains up to 260%.

Author: nwoltman

benchmark/bench-ejs.js

@@ -1,8 +1,9 @@
 'use strict';
 
 var ejs = require('..');
+var path = require('path');
 
-ejs.fileLoader = function(n) { return files[n.replace(/^\//, '').replace(/\.ejs$/, '')]; };
+ejs.fileLoader = function(n) { return files[path.basename(n, '.ejs')]; };
 
 var loops = 10000;
 var runs = 9;  // min 4 for median

lib/ejs.js

@@ -572,7 +572,9 @@ Template.prototype = {
 
     if (!this.source) {
       this.generateSource();
-      prepended += '  var __output = [], __append = __output.push.bind(__output);' + '\n';
+      prepended +=
+        '  var __output = "";\n' +
+        '  function __append(s) { if (s !== undefined && s !== null) __output += s }\n';
       if (opts.outputFunctionName) {
         prepended += '  var ' + opts.outputFunctionName + ' = __append;' + '\n';
       }
@@ -591,7 +593,7 @@ Template.prototype = {
         prepended +=  '  with (' + opts.localsName + ' || {}) {' + '\n';
         appended += '  }' + '\n';
       }
-      appended += '  return __output.join("");' + '\n';
+      appended += '  return __output;' + '\n';
       this.source = prepended + this.source + appended;
     }