when goes on a particular section add a class by jquery code example
Example 1: addclass jquery
$( "p" ).addClass( "myClass yourClass" );
Example 2: jquery addclass
$( "p" ).removeClass( "myClass noClass" ).addClass( "yourClass" );
$( "p" ).addClass( "myClass yourClass" );
$( "p" ).removeClass( "myClass noClass" ).addClass( "yourClass" );