Implement A StringBuilder In JavaScript

I deduced that something that worked in C# should help, if not solve that issue I had with JavaScript. I was right. The code I wrote is here:

String builder for JavaScript

function StringBuilder(value) {
    this.strings = new Array();
    this.append(value);
}
StringBuilder.prototype.append = function(value) {
    if (value) {
        this.strings.push(value);
    }
}
StringBuilder.prototype.clear = function() {
    this.strings.length = 0;
}
StringBuilder.prototype.toString = function() {
    return this.strings.join("");
}
var sb = new StringBuilder();
sb.append("This is");
sb.append("much better looking");
sb.append("than using +=");
// joins the string
var myString = sb.toString();
// Cleans out the string buffer in the StringBuilder.
// This effectively makes it empty in case you did not 
// know what cleaning out a buffer in this context
// meant.
sb.clear();