AutoElipsis.js

// C# version
public static string AutoElipsis(this string text, int maxLength)
{
    if (text == null || text.Length < maxLength)
        return text;

    return text.Substring(0, maxLength-3) + "...";
}

// JS version
if (!String.prototype.autoElipsis) {
  String.prototype.autoElipsis = function(maxLength) {
    if (this == null || this.length < maxLength)
        return this;

    return this.substring(0, maxLength-3) + "...";
  };
}