code: function(needle) {
    // Per spec, the way to identify NaN is that it is not equal to itself
    var findNaN = needle !== needle;
    var indexOf;
  
    if (!findNaN && typeof Array.prototype.indexOf === "function") {
      indexOf = Array.prototype.indexOf;
    } else {
      indexOf = function(needle) {
        var i = -1,
          index = -1;
  
        for (i = 0; i < this.length; i++) {
          var item = this[i];
  
          if ((findNaN && item !== item) || item === needle) {
            index = i;
            break;
          }
        }
  
        return index;
      };
    }
  
    return indexOf.call(this, needle) > -1;
  }
docs: to check if all values in the array are same