Javascript StringBuilder for Beginners (ASP.NET 3.5 and above)

Just a beginner tip. Many programmers still use string concatenations in the classical way. An example situation like this - Adding and deleting div dynamically in JavaScript[^] Are JavaScript strings mutable? NO. So what is the best way to concatenate strings in JavaScript like runtime markup generation, etc? The .NET way is to use StringBuilder. From Framework 3.5, it is available through the Microsoft Ajax Library. Enable Ajax in the page by using a ScriptManager. Now the Sys.StringBuilder class is available for use.

<asp:ScriptManager ID="script1" runat ="server">
 </asp:ScriptManager>

In Javascript:

var sb = new Sys.StringBuilder();
sb.append("Hello ");
sb.append("World ");
alert(sb.toString());

How does a string builder do concatenation efficiently? It uses an array to hold the strings, then uses the Array.Join to concatenate the strings. So intermediate string generations are avoided.