Develop Reference

How to preserve old input text value after the change in Javascript? [duplicate]

I have an input text in jQuery I want to know if it possible to get the value of that input text(type=number and type=text) before the onchange happens and also get the value of the same input input text after the onchange happens. This is using jQuery.
What I tried:
I tried saving the value on variable then call that value inside onchange but I am getting a blank value.

The simplest way is to save the original value using data() when the element gets focus. Here is a really basic example:
JSFiddle: http://jsfiddle.net/TrueBlueAussie/e4ovx435/
$('input').on('focusin', function(){
console.log("Saving value " + $(this).val());
$(this).data('val', $(this).val());
});
$('input').on('change', function(){
var prev = $(this).data('val');
var current = $(this).val();
console.log("Prev value " + prev);
console.log("New value " + current);
});
Better to use Delegated Event Handlers
Note: it is generally more efficient to use a delegated event handler when there can be multiple matching elements. This way only a single handler is added (smaller overhead and faster initialisation) and any speed difference at event time is negligible.
Here is the same example using delegated events connected to document:
$(document).on('focusin', 'input', function(){
console.log("Saving value " + $(this).val());
$(this).data('val', $(this).val());
}).on('change','input', function(){
var prev = $(this).data('val');
var current = $(this).val();
console.log("Prev value " + prev);
console.log("New value " + current);
});
JsFiddle: http://jsfiddle.net/TrueBlueAussie/e4ovx435/65/
Delegated events work by listening for an event (focusin, change etc) on an ancestor element (document* in this case), then applying the jQuery filter (input) to only the elements in the bubble chain then applying the function to only those matching elements that caused the event.
*Note: A a general rule, use document as the default for delegated events and not body. body has a bug, to do with styling, that can cause it to not get bubbled mouse events. Also document always exists so you can attach to it outside of a DOM ready handler :)

Definitely you will need to store old value manually, depending on what moment you are interested (before focusing, from last change).
Initial value can be taken from defaultValue property:
function onChange() {
var oldValue = this.defaultValue;
var newValue = this.value;
}
Value before focusing can be taken as shown in Gone Coding's answer. But you have to keep in mind that value can be changed without focusing.

Just put the initial value into a data attribute when you create the textbox, eg
HTML
<input id="my-textbox" type="text" data-initial-value="6" value="6" />
JQuery
$("#my-textbox").change(function () {
var oldValue = $(this).attr("data-initial-value");
var newValue = $(this).val();
});

I have found a solution that works even with "Select2" plugin:
function functionName() {
$('html').on('change', 'select.some-class', function() {
var newValue = $(this).val();
var oldValue = $(this).attr('data-val');
if ( $.isNumeric(oldValue) ) { // or another condition
// do something
}
$(this).attr('data-val', newValue);
});
$('select.some-class').trigger('change');
}

I found this question today, but I'm not sure why was this made so complicated rather than implementing it simply like:
var input = $('#target');
var inputVal = input.val();
input.on('change', function() {
console.log('Current Value: ', $(this).val());
console.log('Old Value: ', inputVal);
inputVal = $(this).val();
});
If you want to target multiple inputs then, use each function:
$('input').each(function() {
var inputVal = $(this).val();
$(this).on('change', function() {
console.log('Current Value: ',$(this).val());
console.log('Old Value: ', inputVal);
inputVal = $(this).val();
});

my solution is here
function getVal() {
var $numInput = $('input');
var $inputArr = [];
for(let i=0; i < $numInput.length ; i++ )
$inputArr[$numInput[i].name] = $numInput[i].value;
return $inputArr;
}
var $inNum = getVal();
$('input').on('change', function() {
// inNum is last Val
$inNum = getVal();
// in here we update value of input
let $val = this.value;
});

The upvoted solution works for some situations but is not the ideal solution. The solution Bhojendra Rauniyar provided will only work in certain scenarios. The var inputVal will always remain the same, so changing the input multiple times would break the function.
The function may also break when using focus, because of the ▲▼ (up/down) spinner on html number input. That is why J.T. Taylor has the best solution. By adding a data attribute you can avoid these problems:
<input id="my-textbox" type="text" data-initial-value="6" value="6" />

If you only need a current value and above options don't work, you can use it this way.
$('#input').on('change', () => {
const current = document.getElementById('input').value;
}

My business aim was removing classes form previous input and add it to a new one.
In this case there was simple solution: remove classes from all inputs before add
<div>
<input type="radio" checked><b class="darkred">Value1</b>
<input type="radio"><b>Value2</b>
<input type="radio"><b>Value3</b>
</div>
and
$('input[type="radio"]').on('change', function () {
var current = $(this);
current.closest('div').find('input').each(function () {
(this).next().removeClass('darkred')
});
current.next().addClass('darkred');
});
JsFiddle: http://jsfiddle.net/gkislin13/tybp8skL

if you are looking for select droplist, and jquery code would like this:
var preValue ="";
//get value when click select list
$("#selectList").click(
function(){
preValue =$("#selectList").val();
}
);
$("#selectList").change(
function(){
var curentValue = $("#selectList").val();
var preValue = preValue;
console.log("current:"+curentValue );
console.log("old:"+preValue );
}
);

Issues displaying a dynamically updated HTML input value

I'm struggling to get the behaviour I need - as follows:
A HTML form is pre-populated with a value via jQuery. When the user focuses on the input field I want the form to clear. On blur from the form, the form should repopulate the form with the existing value.
I have a solution that clears and repopulates the form but it fails as soon as anything is typed in.
This is what I have so far:
var x = "Default";
$(function () {
$("input").attr({
"value": x
});
$("input").focus(function () {
$("input").attr({
"value": ""
});
});
$("input").blur(function () {
$("input").attr({
"value": x
});
});
});
https://jsfiddle.net/thepeted/p74kfdt8/6/
If I look in developer tools, I can see the input value is changing dynamically in the DOM, but in the case that the user has typed something in to the form, the display no longer updates.
I'd love to understand why this is happening (ie, why it works in one case and not the other). Also, if there is a better way of approaching the problem.

As pointed out by Stijn, best practice would be to use the placeholder attibute.
However if you do want to use a function for it. I would check on the focus if the value is the default value or not. If so, empty the input, if not, don't do anything.
On blur, you also only want to place the default value back if the value is empty... so check for that aswell.
var x = "Default";
$(function() {
$('input[type=text]').val(x);
$('input[type=text]').on('focus', function() {
var elem = $(this);
if (elem.val() == x)
elem.val('');
}).on("blur", function() {
var elem = $(this);
if (elem.val() == '')
elem.val(x);
});
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input type="text" />

Your edited jsfiddle.
updated code:
$("input").blur(function () {
$("input").val(x);
});

Personnaly, I'd use the placeholder attribute as everyone pointed out. If you too are facing the need to support older browsers and some others that do not support the placeholder attribute, use this snippet I've made:
$('input[placeholder]').each(function(){
var $this = $(this);
$this.val($this.attr('placeholder')).css('color','888888');
$this.focus(function(){
if($(this).val() == $(this).attr('placeholder'))
$(this).val('').css('color','');
});
$this.blur(function(){
if($(this).val() == '')
$(this).val($(this).attr('placeholder')).css('color','888888');
});
});
This script will find all inputs with a placeholder attribute, give it's value to the input, and add the correct events. I've left the css calls just to show you where to put the codes to mimic the greyed text like modern browsers do.

Try this code
var x = "Default";
$(function () {
$("input").val(x);
$("input").focus(function () {
$("input").val("");
});
$("input").blur(function () {
$("input").val(x);
});
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<input type="text"/>

Jquery - How to copy an input that has a value on load

I have a website url field that has the value set for returning visitors who have previously filled out the form. If they change the value, then ('keyup blur paste', function() will copy it to a div. If they do not change the value, the ('keyup blur paste', function() does not copy the value to the div
I would like to figure out how to add to this script a function that would also copy the value to the div if they do not change it, because blur only works if they click in the input before they submit the form.
Here is my current script:
$(function () {
$('#Website').on('keyup blur paste', function() {
var self = this;
setTimeout(function() {
var str = $(self).val();
$("#viewer").text(str.replace(/^http\:\/\//, ''));
}, 0)
})
});

If I get you correctly, you want to populate the div on load as well as on keyup/blur/paste? Something like this?
$(function () {
$('#Website').on('keyup blur paste', function() {
var self = this;
setTimeout(function() {
var str = $(self).val();
$("#viewer").text(str.replace(/^http\:\/\//, ''));
}, 0)
});
// just add the line below
$("#viewer").text($('#Website').val().replace(/^http\:\/\//, ''));
});
I've updated the fiddle you created to demonstrate this working: http://jsfiddle.net/8kn4V/2/

on your page load...
$('#mydiv').html('whatever the value of the cookie');
is that what you need? as they mentioned in the comments above, your question is a little confusing.

use val() for input , select and textareas, and use text() for general elements like divs.
First solution
It seems now you are using a timeout of 0. That is not necessary at all, I think. So please check out this Fiddle:
$('#website').on("keyup blur paste", function () {
var s = $(this).text();
$("#viewer").text(s.replace(/^http\:\/\//, ''));
});
Edited solution
Now it seems you also want code that update #viewer from #website even when not triggered.
Here is a second fiddle — I hope you'll give credit if this solves the problem as it stands currently.
Relevant code:
function viewerupdate(me){
var s = me.text();
$("#viewer").text(s.replace(/^http\:\/\//, ''));
}
$('#website').on("keyup blur paste", function () { viewerupdate($(this)) });
var current_viewer = $('#viewer').text();
$('#submit').click(function(){ // assumes in the case that no change was made, that the submission is done through #submit
if($('#viewer').text() == current_viewer )
viewerupdate($('#website'));
});

jQuery, how to capture when text input has changed as a result of another event

I have a text input that is updated as a result of a button event. I would like to detect when the value in the text input has changed. See the example below:
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script>
<script type="text/javascript">
$(document).ready(function(){
$('#text').bind("input change paste", function(){
console.log("text changed");
// do something
});
$('#click').click (function(){
$('#text').val('something');
});
});
</script>
<body>
<input id='text' type='text'>
<input id='click' type='button' value='click'>
</body>
Later on, that button will trigger a calender so the user select a date/time which will update the text input. Since the calender is part of a library we I don't want to change it. I would like to detect when the text field gets a new value.
thanks!

I think what you're referring to is
$("#text").on("change", function(){});
take a look at this post

Since the date/time picker library you are using doesn't raise any sort of change or input event, the only way to reliable tell if the value has changed is to watch with a timer and raise the change event yourself. The following is one way to do this:
// check for changes every 100 ms
setInterval(function() {
var lastVal = $('#text').data('last-value');
if (typeof lastVal === 'undefined') {
lastVal = $('#text').val();
$('#text').data('last-value', lastVal);
}
if (lastVal !== $('#text').val()) {
$('#text').change(); // trigger the change event
}
}, 100);
// setup your change handler
$('#text').on("input change paste", function() {
// before doing anything else, set the last-value data property
$('#text').data('last-value', $('#text').val());
// do something ...
console.log('changed!');
});
// now programmitically updating the $('#text') element will result
// in your change handler being triggered
$('#click').click (function(){
$('#text').val('something');
});

How to know with jQuery that a "select" input value has been changed?

I know that there is the change event handling in jQuery associated with an input of type select. But I want to know if the user has selected another value in the select element ! So I don't want to run code when the user select a new element in the select but I want to know if the user has selected a different value !
In fact there are two select elements in my form and I want to launch an ajax only when the two select elements has been changed. So how to know that the two elements has been changed ?

You can specifically listen for a change event on your chosen element by setting up a binding in your Javascript file.
That only solves half your problem though. You want to know when a different element has been selected.
You could do this by creating a tracking variable that updates every time the event is fired.
To start with, give your tracking variable a value that'll never appear in the dropdown.
// Hugely contrived! Don't ship to production!
var trackSelect = "I am extremely unlikely to be present";
Then, you'll need to set up a function to handle the change event.
Something as simple as:-
var checkChange = function() {
// If current value different from last tracked value
if ( trackSelect != $('#yourDD').val() )
{
// Do work associated with an actual change!
}
// Record current value in tracking variable
trackSelect = $('#yourDD').val();
}
Finally, you'll need to wire the event up in document.ready.
$(document).ready(function () {
$('#yourDD').bind('change', function (e) { checkChange() });
});

First of all you may use select event handler (to set values for some flags). This is how it works:
$('#select').change(function () {
alert($(this).val());
});​
Demo: http://jsfiddle.net/dXmsD/
Or you may store the original value somewhere and then check it:
$(document).ready(function () {
var val = $('#select').val();
...
// in some event handler
if ($('#select').val() != val) ...
...
});

First you need to store previous value of the selected option, then you should check if new selected value is different than stored value.
Check out the sample!
$(document).ready(function() {
var lastValue, selectedValue;
$('#select').change(function() {
selectedValue = $(this).find(':selected').val();
if(selectedValue == lastValue) {
alert('the value is the same');
}
else {
alert('the value has changed');
lastValue = selectedValue;
}
});
});​

You can save the value on page load in some hidden field.
like
$(document).ready(function(){
$('hiddenFieldId').val($('selectBoxId').val());
then on change you can grab the value of select:
});
$('selectBoxId').change(function(){
var valChng = $(this).val();
// now match the value with hidden field
if(valChng == $('hiddenFieldId').val()){
}
});

$("select").change(function () {
var str = "";
$("select option:selected").each(function () {
str += $(this).text() + " ";
});
$("div").text(str);
})
.change();
http://docs.jquery.com/Events/change