jquery code to get input form value_jquery

jquery gets the value of the radio radio button
$("input[name='items']:checked").val();
jquery radio gets the value, checkbox gets the value, select Get value, radio selected, checkbox selected, select selected, and related
Get the value of a set of radio selected items
var item = $('input[name=items][checked ]').val();
Get the text of the 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 radio selection group The second element is the currently selected value
$('input[name=items]').get(1).checked = true;

Get the value:

Text box, text area: $("#txt").attr("value");
Multiple selection box checkbox: $("#checkbox_id").attr("value");
Radio selection group radio: $("input[type=radio][checked]").val();
drop-down box select: $('#sel').val();

control Form element:
Text box, text area: $("#txt").attr("value",'');//Clear content
$("#txt").attr( "value",'11');//Fill content

Multiple selection box checkbox: $("#chk1").attr("checked",'');//Uncheck
$("#chk2").attr("checked",true);//Check
if($("#chk1").attr('checked')==undefined) //Determine whether it has been checked Check

radio group radio: $("input[type=radio]").attr("checked",'2');//Set the item with value=2 as the currently selected item
Drop-down box select: $("#sel").attr("value",'-sel3');//Set the item with value=-sel3 as the currently selected item
$("1111 2222").appendTo("#sel")//Add the option of the drop-down box
$("#sel").empty();//Clear the drop-down box

I just started to get in touch with jquery and I am not familiar with many things
When I used $("#id") to get the input element of the page, I found that $("#id").value cannot get the value

Later, with the help of the great Baidu, I finally found the cause of the problem:
$("") is a jquery object, not a dom element

value is an attribute of dom element

Jquery corresponds to val

val(): Get the current value of the first matching element.

val(val): Set the value of each matching element.

So, the code should be written like this:

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

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