javascript StringBuilder类实现

　　// Initializes a new instance of the StringBuilder class

　　// and appends the given value if supplied

　　function StringBuilder(value)

　　{

　　this.strings = new Array("");

　　this.append(value);

　　}

　　// Appends the given value to the end of this instance.

　　StringBuilder.prototype.append = function (value)

　　{

　　if (value)

　　{

　　this.strings.push(value);

　　}

　　}

　　// Clears the string buffer

　　StringBuilder.prototype.clear = function ()

　　{

　　this.strings.length = 1;

　　}

　　// Converts this instance to a String.

　　StringBuilder.prototype.toString = function ()

　　{

　　return this.strings.join("");

　　}

　　// create a StringBuilder

　　var sb = new StringBuilder();

　　// append some text

　　sb.append("Some of those preparing for international ");

　　sb.append("exams such as the TOEFL ");

　　sb.append("need extra practice for the listening section");

　　// get the full string value

　　var s = sb.toString();

　　alert(s);