Are JavaScript strings immutable? Do I need a “string builder” in JavaScript?

Question

Does javascript use immutable or mutable strings? Do I need a \"string builder\"?

Answer 1

Regarding your question (in your comment to Ash's response) about the StringBuilder in ASP.NET Ajax the experts seem to disagree on this one.

Christian Wenz says in his book Programming ASP.NET AJAX (O'Reilly) that "this approach does not have any measurable effect on memory (in fact, the implementation seems to be a tick slower than the standard approach)."

On the other hand Gallo et al say in their book ASP.NET AJAX in Action (Manning) that "When the number of strings to concatenate is larger, the string builder becomes an essential object to avoid huge performance drops."

I guess you'd need to do your own benchmarking and results might differ between browsers, too. However, even if it doesn't improve performance it might still be considered "useful" for programmers who are used to coding with StringBuilders in languages like C# or Java.