String concatenation in JavaScript

string_concatenation.js

function StringBuffer() {
  this.__strings__ = new Array;
}

StringBuffer.prototype.append = function(str) {
  this.__strings__.push(str);
};

StringBuffer.prototype.toString = function() {
  return this.__strings__.join(" ");
};

var d1 = new Date();
var str = "";
for (var i=0; i<1000000; i++) {
  str += "text";
}
var d2 = new Date();

document.write("Concatenation with a plus: " + (d2.getTime() - d1.getTime()) + " milliseconds </br>")

var oBuffer = new StringBuffer();
d1 = new Date();
for (var i=0; i<1000000; i++) {
  oBuffer.append("text");
}
d2 = new Date();
document.write("Concatenation with a StringBuffer: " + (d2.getTime() - d1.getTime()) + " milliseconds")