code: function( array, searchElement, fromIndex ) {
              if ( Array.prototype.indexOf ) {
                  this.indexOf = function( array, searchElement, fromIndex ) {
                      return array.indexOf( searchElement, fromIndex );
                  };
              } else {
                  this.indexOf = function( array, searchElement, fromIndex ) {
                      var i,
                          pivot = ( fromIndex ) ? fromIndex : 0,
                          length;
                      if ( !array ) {
                          throw new TypeError( );
                      }
  
                      length = array.length;
                      if ( length === 0 || pivot >= length ) {
                          return -1;
                      }
  
                      if ( pivot < 0 ) {
                          pivot = length - Math.abs( pivot );
                      }
  
                      for ( i = pivot; i < length; i++ ) {
                          if ( array[i] === searchElement ) {
                              return i;
                          }
                      }
                      return -1;
                  };
              }
              return this.indexOf( array, searchElement, fromIndex );
          }
docs: Find the first index at which an element is found in an array or -1
  if not present.
  
  Code taken and adapted from
  https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/indexOf#Compatibility
  
  @function
  @param {Array} array The array from which to find the element
  @param {Object} searchElement The element to find
  @param {Number} [fromIndex=0] Index to start research.
  @returns {Number} The index of the element in the array.