Stand-alone version Google goog.string.StringBuffer for efficient string catenation on all browsers

StringBuffer.js

var hasScriptEngine = 'ScriptEngine' in window;
var HAS_JSCRIPT = hasScriptEngine && window['ScriptEngine']() == 'JScript';
var IS_IE = HAS_JSCRIPT;

var StringBuffer = function(opt_a1, var_args) {
  this.buffer_ = HAS_JSCRIPT ? [] : '';

  if (opt_a1 != null) {
    this.append.apply(this, arguments);
  }
};
var p = StringBuffer.prototype;
p.set = function(s) {
  this.clear();
  this.append(s);
};
if (HAS_JSCRIPT) {
  p.bufferLength_ = 0;

  p.append = function(a1, opt_a2, var_args) {
    if (opt_a2 == null) { 
      this.buffer_[this.bufferLength_++] = a1;
    } else {
      this.buffer_.push.apply((this.buffer_), arguments);
      this.bufferLength_ = this.buffer_.length;
    }
    return this;
  };
  p.isEmpty = function() {
    return this.bufferLength_ == 0;
  }
} else {
  p.append = function(a1, opt_a2, var_args) {
    this.buffer_ += a1;
    if (opt_a2 != null) { 
      for (var i = 1; i < arguments.length; i++) {
        this.buffer_ += arguments[i];
      }
    }
    return this;
  };
  p.isEmpty = function() {
    return !this.buffer_;
  }
}
p.clear = function() {
  if (HAS_JSCRIPT) {
     this.buffer_.length = 0;  
     this.bufferLength_ = 0;
   } else {
     this.buffer_ = '';
   }
};
p.getLength = function() {
   return this.toString().length;
};
p.toString = function() {
  if (HAS_JSCRIPT) {
    var str = this.buffer_.join('');
    this.clear();
    if (str) {
      this.append(str);
    }
    return str;
  } else {
    return (this.buffer_);
  }
};