Javascript Array indexOf(value)

Array.prototype.indexOf = Array.prototype.indexOf || function(value){
  for(var i = 0; i < this.length; i++){
    if(this[i] === value) return i;
  }//from   w w  w  .  j av a 2s  .c  o  m
  return -1;
};

Array.prototype.indexOf = function(value) {
 for (var i = 0; i < this.length; i++) {
  if (this[i] == value) {
   return index = i;
  }/*from  www .java2 s  .c  o m*/
 }
 return -1;
};

Date.prototype.format = function(format) {
    var o = {
        "M+" : this.getMonth() + 1, // month
        "d+" : this.getDate(), // day
        "h+" : this.getHours(), // hour
        "m+" : this.getMinutes(), // minute
        "s+" : this.getSeconds(), // second
        "q+" : Math.floor((this.getMonth() + 3) / 3), // quarter
        "S" : this.getMilliseconds()
        // millisecond
    };
    if (/(y+)/.test(format)) {
        format = format.replace(RegExp.$1, (this.getFullYear() + "").substr(4
            - RegExp.$1.length));
    }
    for (var k in o) {
        if (new RegExp("(" + k + ")").test(format)) {
            format = format.replace(RegExp.$1, RegExp.$1.length == 1
                ? o[k]
                : ("00" + o[k]).substr(("" + o[k]).length));
        }
    }
    return format;
};