jquery method to get element value (common form elements)_jquery

jquery radio value, checkbox value, select 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;
The second element of the radio radio selection 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");
Single selection group radio: $("input[@type=radio][@ checked]").val();
Drop-down box select: $('#sel').val();

Control form elements:
Text box, text area: $(" #txt").attr("value",'');//Clear content
$("#txt").attr("value",'11');//Fill content

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

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
$("11112222").appendTo("#sel") //Add the option of the drop-down box
$("#sel").empty(); //Clear the drop-down box