Javascript Array myFilter( callback ) method

var names = [ 'Lars', 'Jan', 'Peter', 'Bo', 'Iso', 'Maz', 'Ib' ];

function upperCasename( name )
{
 return name.toUpperCase();
}

function checkName( name )
{
 if( name.length <= 3 )
 {
  return name;
 }
}

Array.prototype.myFilter = function myFilter( callback )
{

 var filteredArray = [];

 for( var i = 0; i < this.length; i++ )
 {
  if( callback( this[ i ] ) )
  {/* w w  w. j  av  a 2 s. co m*/
   filteredArray.push( callback( this[ i ] ) );
  }
 }

 return filteredArray;

};

var newArray = names.myFilter( upperCasename );
var newArray2 = names.myFilter( checkName );

console.log( newArray );
console.log( newArray2 );