A collection of convenient JavaScript-prototypes

array.prototypes.js

// Internet Explorer did not support indexOf until IE9
if (!Array.prototype.indexOf)
{
  Array.prototype.indexOf = function(elt /*, from*/)
  {
    var len = this.length >>> 0;

    var from = Number(arguments[1]) || 0;
    from = (from < 0)
         ? Math.ceil(from)
         : Math.floor(from);
    if (from < 0)
      from += len;

    for (; from < len; from++)
    {
      if (from in this &&
          this[from] === elt)
        return from;
    }
    return -1;
  };
}

date.prototypes.js

// Add or subtract days from the date object
Date.prototype.addDays = function (days) {
    this.setDate(this.getDate() + days);
    return this;
};

// Return date as a string with format yyyy-mm-dd
Date.prototype.asShortDate = function () {
    var dd = this.getDate();
    var mm = this.getMonth() + 1;
    var y = this.getFullYear();

    mm = (mm < 10) ? "0" + mm : mm;
    dd = (dd < 10) ? "0" + dd : dd;

    return y + "-" + mm + "-" + dd;
};

string.prototypes.js

// Split a string into an array on camel case
String.prototype.splitOnCamelCase = function () {
    return this.match(/([A-Z]?[^A-Z]*)/g).slice(0, -1);
}