Jquery code for retrieving input form values

jquery Fetch Radio The value of the radio button
$ ("Input[name= ' Items ']:checked"). Val ();
jquery Radio value, checkbox value, select Value, Radio selected, CheckBox selected, select selected, and related
Gets the value of a set of radio selected items
var item = $ (' input[name=items][checked] '). Val ();
Gets the text of the Select selected item
var item = $ ("Select[name=items] option[selected]"). Text ();
The second element of the Select Drop-down box is the currently selected value
$ (' #select_id ') [0].selectedindex = 1;
Radio the second element of a radio group is the currently selected value
$ (' input[name=items] '). Get (1). checked = true;

Get Value:

text box, text area: $ ("#txt"). attr ("value");
Multiple-selection box checkbox:$ ("#checkbox_id"). attr ("value");
Radio Group Radio: $ ("input[type=radio][checked]"). Val ();
Dropdown box Select: $ (' #sel '). Val ();

Control form elements:
text box, text area: $ ("#txt"). attr ("Value", "");/empty content
$ ("#txt"). attr ("value", ' 11 ');//fill content

Multi-Marquee checkbox: $ ("#chk1"). attr ("Checked", "");/no tick.
$ ("#chk2"). attr ("Checked", true);/tick
if ($ ("#chk1"). attr (' checked ') ==undefined)//judge whether it has been ticked

Radio Group Radio: $ ("Input[type=radio]"). attr ("Checked", ' 2 ');//Set value=2 project is currently selected
Dropdown box Select: $ ("#sel"). attr ("value", '-sel3 ');//Set VALUE=-SEL3 item as current selection
$ ("<option value= ' 1 ' >1111</option><option value= ' 2 ' >2222</option>"). Appendto ("#sel")// Option to add a drop-down box
$ ("#sel"). empty ();//Empty Drop-down box

Just beginning to touch jquery, a lot of things are unfamiliar
When you use $ ("#id") to get the input element of the page, $ ("#id") is found. Value cannot be fetched

Finally, with the help of the great Baidu, found the cause of the problem:
$ ("") is a jquery object, not a DOM element

Value is a property of DOM element

jquery corresponds to Val.

Val (): Gets the current value of the first matching element.

Val (val): Sets the value of each matching element.

So the code should write this:

Value: val = $ ("#id") [0].value;
Assign value:
$ ("#id") [0].value = "New value";
or $ ("#id"). Val ("new value");

Or this can also be: val = $ ("#id"). attr ("value");