filter() method performs a function (
callback_function) on every element in that array (
array_name). It results in the creation of a new array. Only when the return value of the
true, will that value be added to the new array.
callback_function() is invoked only for indexes of the array which have assigned values. The
callback_function() is not invoked for indexes that have been deleted or that have never been assigned a value. Array elements which do not pass the
callback_function() test are skipped, and are not included in the new array.
callback_function creates a new array element from an element of the current array.
argument_name is an object to be used as
this when executing the
callback_function. The second parameter,
argument_name, is seldom used.