Create StringBuilder.js

var str = new String('0'),
    	builder = str.StringBuilder()
			         .append('1')
			         .append('2')
			         .append('3');
			                 
	console.log(builder.toString());

	builder.insert(0,'5')
	       .remove(2,1);

	console.log(builder.toString());

	builder.clear();

	console.log(builder.toString());