Implementation Code of jQuery operation input type = checkbox

Copy codeThe Code is as follows:
<Input type = "checkbox">:
The international team that qualify for the 2012 European Cup "death group" is: <br>
<Input type = "checkbox" name = "nation" value = "Germany"> Germany
<Input type = "checkbox" name = "nation" value = "Denmark"> Denmark
<Input type = "checkbox" name = "nation" value = "Holland"> Netherlands
<Input type = "checkbox" name = "nation" value = "Portugal"> Portugal

1. The first and second place in the group can only be selected.
Copy codeThe Code is as follows:
Var len = $ ("input [name = 'nation']: checked"). length;
If (len = 0 ){
Alert ("select the qualifying National Team! ");
Return false;
} Else if (len <2 ){
Alert ("select two national teams! ");
Return false;
} Else if (len> 2 ){
Alert ("Only two national teams can be selected! ");
Return false;
} Else {
Return true;
}

2. Traverse selected national teams.
Copy codeThe Code is as follows:
$ ("Input [name = 'nation']: checked"). each (function (){
Alert ("selected national team:" + $ (this). val ());
});

3. Cancel all selected national teams.
Copy codeThe Code is as follows: $ ("input [name = 'nation']: checked"). attr ("checked", false );
4. Select two national teams.
Copy codeThe Code is as follows:
$ ("Input [name = 'nation'] [value = 'Germany ']"). attr ("checked", true );
$ ("Input [name = 'nation'] [value = 'holand']"). attr ("checked", true );

5. You are not allowed to select the National Team.
Copy codeThe Code is as follows: $ ("input [name = 'nation']"). attr ("disabled", true );
6. Select the National Team.
Copy codeThe Code is as follows: $ ("input [name = 'nation']"). attr ("disabled", false );
7. Select the national team with an even or odd number of indexes (the index starts from 0 ).
Copy codeThe Code is as follows: // select the national team with an even Index
$ ("Input [name = 'nation']: even"). attr ("checked", true );
// Select the national team with an odd Index
$ ("Input [name = 'nation']: odd"). attr ("checked", true );