Get all ID of input box that contains a class

Question 1

I want to alert all the ID that contains the class failed after pushing a button or a command.

Use class selector to get elements with particular class. You can use each() to traverse all the element. Bind the click event to button, you can use button id in id selector to bind the event.

Live Demo

Html

<input id="first" class="failed" />
<input id="last" class="failed" />
<input id="city" class="failed" />
<input id="state" class="failed" />
<input type="button" id="btn" value="click" />

Javascript

$('#btn').click(function () {
    $('.failed').each(function () {
        alert(this.id);
    });
});

Question 2

You can use .map() to get an array of ids

var ids = $('.failed').map(function(){
    return this.id
}).get();

console.log(ids);
alert(ids)

Question 3

use each jquery

$('.failed').each(function(e){
        var id=$(this).attr('id');//find each id 
});

Question 4

$.each($('.failed'), function () {alert ($(this).attr('id')); });

Question 5

var ids = []; //create an array
$('.failed').each(function(e)){   //iterate each class
    ids.push($(this).prop('id')); //push their id to array
});
alert(ids);

Question 6

You could iterate through the inputs and do what ever you want with elements that have the defined class:

$("input.failed").each(function() {
  console.log($(this).attr('id'));
});

Question 7

You can alert all ids on button click like this:

$("#btnid").click(function(){    //click on button
    $('.failed').each( function () {
       alert ($(this).attr('id')); //alert id one by one
  });
});