function arrayIntersection ( a, b )  {      var ai=0, bi=0;      var result = new Array();      while ( ai < a.length && bi < b.length )      {          if      ( a[ai] < b[bi] ) { ai++; }          else if ( a[ai] > b[bi] ) { bi++; }          else /* they're equal */          {              result.push ( a[ai] );              ai++;              bi++;          }      }      return result;  }  console.log ( arrayIntersection ( [1,2,3],[2,3,4,5,6] ) );//[2,3]