You are currently viewing the BOOK: Professional JavaScript for Web Developers ISBN: 978-0-7645-7908-0 section of the Wrox p2p Programmer to Programmer discussion community. This is a community of more than 40,000 computer programmers including Wrox book authors and readers. As a guest, you can read any forum posting. By joining our free Wrox p2p community you can post your own programming questions and respond to other programmers’ questions. Registered users also don't have to see the ads that are displayed to guests. Registration is fast, simple and absolutely free so please, join today!
Join today and post to win prizes! Post more to increase your chances of being Wrox’s top poster of the month.
I have just copied down the code for the StringBuffer "class" performance comparison on pgs 97-98 of the book but my results are opposite to what the book is explaining. The += operation without using the StringBuffer class is actually running significantly faster. Here is the code:
Code:
function StringBuffer1() {
this._strings = new Array;
if (typeof StringBuffer1._initialized == "undefined") {
StringBuffer1.prototype.append = function (str) {
this._strings.push(str)
};
StringBuffer1.prototype.toString = function () {
return this._strings.join("");
};
StringBuffer1._initialized = true;
};
};
function StringBuffer2() {
this._strings = new Array;
};
StringBuffer2.prototype.append = function (str) {
this._strings.push(str)
};
StringBuffer2.prototype.toString = function () {
return this._strings.join("");
};
var d1 = new Date();
var str = "";
for (var i=0; i < 10000; i++) {
str += "text";
}
var d2 = new Date();
document.write("Concatenation with plus: " + (d2.getTime() - d1.getTime()) + " milliseconds<br />");
var oBuffer = new StringBuffer1();
d1 = new Date();
for (var i=0; i < 10000; i++) {
oBuffer.append("text");
}
var sResult = oBuffer.toString();
d2 = new Date();
document.write("Concatenation with StringBuffer1: " + (d2.getTime() - d1.getTime()) + " milliseconds<br />");
var oBuffer = new StringBuffer2();
d1 = new Date();
for (var i=0; i < 10000; i++) {
oBuffer.append("text");
}
var sResult = oBuffer.toString();
d2 = new Date();
document.write("Concatenation with StringBuffer2: " + (d2.getTime() - d1.getTime()) + " milliseconds<br />");
results:
Concatenation with plus: 12 milliseconds
Concatenation with StringBuffer1: 23 milliseconds
Concatenation with StringBuffer2: 26 milliseconds
I do have the 2005 version of the text, so I don't know if something has been changed with javascript since this publication. I'm also using Firefox 3.0.14 right now.
Last edited by IAmCorbin : October 26th, 2009 at 04:27 AM.
Chapter 3 - StringBuffer vs += Performance Issue
Linear Mode
