Giant Geek Blog

Eventually, you come to a point where the performance of JavaScript becomes an issue.  Most modern browsers have made significant improvements  in their javascript engines, unfortunately Microsoft has yet to do the same.  MSIE’s (at least up to and including MSIE8)  javascript performance lags far behind Mozilla/Firefox, Safari, Chrome and Opera.

String concatenation is extremely slow in MSIE,  but arrays are generally fast… as such it’s often beneficial to implement an object similar to the Java StringBuffer (or StringBuilder) for JavaScript.

The StringBuffer implementation… you can customize to make it more functional, but this is the core:

function StringBuffer(){
this.buffer = [];
}
StringBuffer.prototype.append = function append(string){
this.buffer.push(string);
return this;
};
StringBuffer.prototype.toString = function toString(){
return this.buffer.join(”");
};

Example:

function example_slow(x1,x2,x3){
var rc = x1;
rc+=x2;
rc+=x3;
return rc;
}

function example_fast(x1,x2,x3){
var sb = new StringBuffer();
sb.append(x1);
sb.append(x2);
sb.append(x3);
return sb.toString();
}

References:

• http://www.softwaresecretweapons.com/jspwiki/javascriptstringconcatenation
• http://social.msdn.microsoft.com/Forums/en-US/iewebdevelopment/thread/72429b15-73e2-4b4e-9288-9e1dfd47858b
• http://freecode-freecode.blogspot.com/2007/05/javascript-stringbuffer-like-java.html
• http://www.java2s.com/Tutorial/JavaScript/0120__String/StringBufferbasedonarray.htm
• http://www.irt.org/script/1699.htm

Cheers