The value assignment implementation code of CheckBox, RadioButton, DropDownList in jquery

Since the version of jquery has been updated very quickly, the code has changed a lot, the following jquery code is suitable for query1.4 version above
Radio

1. To get the selected value, three methods are available:
$ (' input:radio:checked '). Val ();
$ ("input[type= ' Radio ']:checked"). Val ();
$ ("Input[name= ' rd ']:checked"). Val ();
2. Set the first radio to the selected value:
$ (' Input:radio:first '). attr (' checked ', ' checked ');
Or
$ (' Input:radio:first '). attr (' checked ', ' true ');
Note: attr ("Checked", ' checked ') = attr ("Checked", ' true ') = attr ("Checked", true)
3. Set the last radio as the selected value:
$ (' Input:radio:last '). attr (' checked ', ' checked ');
Or
$ (' Input:radio:last '). attr (' checked ', ' true ');
4. Set any one of the radio to the selected value according to the index value:
$ (' Input:radio '). EQ (index value). attr (' checked ', ' true '); index value =0,1,2 ....
Or
$ (' Input:radio '). Slice. attr (' checked ', ' true ');
5. Set Radio to the selected value based on value
$ ("input:radio[value= ' Rd2 ')"). attr (' checked ', ' true ');
Or
$ ("input[value= ' Rd2 ')"). attr (' checked ', ' true ');
6. Remove Radio with value Rd2
$ ("input:radio[value= ' Rd2 ')". Remove ();
7. Delete the first few radio
$ ("Input:radio"). EQ (index value). Remove (); index value =0,1,2 ....
such as removing the 3rd radio:$ ("Input:radio"). EQ (2). Remove ();
8. Traverse Radio
$ (' Input:radio '). each (function (Index,domele) {
Write code
});

DropDownList

1. Get the check:
Gets the value of the selected item:
$ (' Select#sel option:selected '). Val ();
Or
$ (' Select#sel '). Find (' option:selected '). Val ();
Gets the text value of the selected item:
$ (' select#seloption:selected '). Text ();
Or
$ (' Select#sel '). Find (' option:selected '). Text ();
2. Gets the index value of the currently selected item:
$ (' Select#sel '). Get (0). SelectedIndex;
3. Get the maximum index value for the current option:
$ (' Select#sel option:last '). attr ("index")
4. Get the length of the DropDownList:
$ (' Select#sel ') [0].options.length;
Or
$ (' Select#sel '). Get (0). Options.length;
5. Set the first option to a selected value:
$ (' Select#sel option:first '). attr (' selected ', ' true ')
Or
$ (' Select#sel ') [0].selectedindex = 0;
6. Set the last option to the selected value:
$ (' Select#sel option:last). attr (' selected ', ' true ')
7. Set any option to the selected value according to the index value:
$ (' Select#sel ') [0].selectedindex = index value; index value =0,1,2 ....
8. Set option for Value=4 to the selected value:
$ (' Select#sel '). attr (' Value ', ' 4 ');
Or
$ ("Select#sel option[value= ' 4 ']"). attr (' selected ', ' true ');
9. Delete the value=3 option:
$ ("Select#sel option[value= ' 3 ']"). Remove ();
10. Delete the first few option:
$ ("Select#sel option"). EQ (index value). Remove (); index value =0,1,2 ....
If you delete a 3rd radio:
$ ("Select#sel option"). EQ (2). Remove ();
11. Delete the first option:
$ ("Select#sel option"). EQ (0). Remove ();
Or
$ ("Select#sel Option:first"). Remove ();
12. Delete the last option:
$ ("Select#sel option:last"). Remove ();
13. Delete DropDownList:
$ ("Select#sel"). Remove ();
14. Add an option after the select:
$ ("Select#sel"). Append ("<option value= ' 6 ' >f</option>");
15. Add an option in front of select:
$ ("Select#sel"). Prepend ("<option value= ' 0 ' >0</option>");
16. Traverse option:
$ (' select#sel option '). each (function (index, domele) {
Write code
});

CheckBox

1. Get a single checkbox check (three ways):
$ ("input:checkbox:checked"). Val ()
Or
$ ("input:[type= ' checkbox ']:checked"). Val ();
Or
$ ("input:[name= ' ck ']:checked"). Val ();
2. Get multiple checkbox-checked items:
$ (' Input:checkbox '). each (function () {
if ($ (this). attr (' checked ') ==true) {
Alert (This). Val ());
}
});
3. Set the first checkbox to the selected value:
$ (' Input:checkbox:first '). attr ("Checked", ' checked ');
Or
$ (' Input:checkbox '). EQ (0). attr ("Checked", ' true ');
4. Set the last checkbox to the selected value:
$ (' Input:radio:last '). attr (' checked ', ' checked ');
Or
$ (' Input:radio:last '). attr (' checked ', ' true ');
5. Set any checkbox to the selected value according to the index value:
$ (' Input:checkbox). EQ (index value). attr (' checked ', ' true '); index value =0,1,2 ....
Or
$ (' Input:radio '). Slice. attr (' checked ', ' true ');
6. Select multiple checkboxes:
Check both the 1th and 2nd checkboxes:
$ (' Input:radio '). Slice (0,2). attr (' checked ', ' true ');
7. Set the checkbox to the selected value based on value:
$ ("input:checkbox[value= ' 1 ']"). attr (' checked ', ' true ');
8. Delete the Value=1 checkbox:
$ ("input:checkbox[value= ' 1 ']"). Remove ();
9. Delete the first few checkboxes:
$ ("Input:checkbox"). EQ (index value). Remove (); index value =0,1,2 ....
To delete a 3rd checkbox:
$ ("Input:checkbox"). EQ (2). Remove ();
10. Traverse the checkbox:
$ (' Input:checkbox '). each (function (index, domele) {
Write code
});
11. Select All
$ (' Input:checkbox '). each (function () {
$ (this). attr (' checked ', true);
});
12. Cancel All selections:
$ (' Input:checkbox '). each (function () {
$ (this). attr (' checked ', false);
});

The value assignment implementation code of CheckBox, RadioButton, DropDownList in jquery