Is there any way I can create a constant function that listens to an input, so when that input value changes, something is triggered immediately?
I am looking for something using pure javascript, no plugins, no frameworks and I can't edit the HTML.
Something, for example:
When I change the value in the input MyObject, this function runs.
Any help?
This is what events are for.
HTMLInputElementObject.addEventListener('input', function (evt) {
something(this.value);
});
As a basic example...
HTML:
<input type="text" name="Thing" value="" />
Script:
/* event listener */
document.getElementsByName("Thing")[0].addEventListener('change', doThing);
/* function */
function doThing(){
alert('Horray! Someone wrote "' + this.value + '"!');
}
Here's a fiddle: http://jsfiddle.net/Niffler/514gg4tk/
Actually, the ticked answer is exactly right, but the answer can be in ES6 shape:
HTMLInputElementObject.oninput = () => {
console.log('run'); // Do something
}
Or can be written like below:
HTMLInputElementObject.addEventListener('input', (evt) => {
console.log('run'); // Do something
});
Default usage
el.addEventListener('input', function () {
fn();
});
But, if you want to fire event when you change inputs value manualy via JS you should use custom event(any name, like 'myEvent' \ 'ev' etc.) IF you need to listen forms 'change' or 'input' event and you change inputs value via JS - you can name your custom event 'change' \ 'input' and it will work too.
var event = new Event('input');
el.addEventListener('input', function () {
fn();
});
form.addEventListener('input', function () {
anotherFn();
});
el.value = 'something';
el.dispatchEvent(event);
https://developer.mozilla.org/en-US/docs/Web/Guide/Events/Creating_and_triggering_events
Another approach in 2021 could be using document.querySelector():
const myInput = document.querySelector('input[name="exampleInput"]');
myInput.addEventListener("change", (e) => {
// here we do something
});
This sounds exactly like the problem I had.
And I would have stated the same question, but I guess it's the same wrong question...
IMHO it's just 'onchange' mistaken as 'oninput' which are 2 different things.
Give me a lot of minus for this statement, I dont care, but I guess it may help one or the other ...
HTML form input contain many events. Refer from MDN document, on the sidebar go to Events menu and expand it. You will see many useful events such as beforeinput, change, copy, cut, input, paste, and drag drop events.
iput & change.
The beforeinput, and input events are fired by order when you type the form input value.
When the form input value has changed and you lost focus on that input, the change event is fired.
Cut, copy, paste.
When you cut (CTRL+X on keyboard shortcut) the input value, the cut, beforeinput, input events are fired.
When you copy (CTRL+C on keyboard shortcut), the copy event is fired alone.
When you paste the value from clipboard (CTRL+V on keyboard shortcut), the paste, beforeinput, input events are fired.
JS change value.
To change input value by JavaScript and make important events work, you need to dispatch at least 2 events by order. One is input and two is change. So that you can focus your code to listened to input or change event. It's easier this way.
Here is all sample code.
(() => {
let inputText = document.getElementById('text');
let submitBtn = document.getElementById('submit');
let triggerJSBtn = document.getElementById('button');
submitBtn.addEventListener('click', (event) => {
event.preventDefault(); // just prevent form submitted.
});
triggerJSBtn.addEventListener('click', (event) => {
const thisTarget = event.target;
event.preventDefault();
inputText.value = thisTarget.innerText;
inputText.dispatchEvent(new Event('input'));
inputText.dispatchEvent(new Event('change'));
});
inputText.addEventListener('beforeinput', (event) => {
const thisTarget = event.target;
console.log('beforeinput event. (%s)', thisTarget.value);
});
inputText.addEventListener('input', (event) => {
const thisTarget = event.target;
console.log('input event. (%s)', thisTarget.value);
});
inputText.addEventListener('change', (event) => {
const thisTarget = event.target;
console.log('change event. (%s)', thisTarget.value);
});
inputText.addEventListener('cut', (event) => {
const thisTarget = event.target;
console.log('cut event. (%s)', thisTarget.value);
});
inputText.addEventListener('copy', (event) => {
const thisTarget = event.target;
console.log('copy event. (%s)', thisTarget.value);
});
inputText.addEventListener('paste', (event) => {
const thisTarget = event.target;
console.log('paste event. (%s)', thisTarget.value);
});
})();
/* for beautification only */
code {
color: rgb(200, 140, 50);
}
small {
color: rgb(150, 150, 150);
}
<form id="form">
<p>
Text: <input id="text" type="text" name="text">
</p>
<p>
Text 2: <input id="text2" type="text" name="text2"><br>
<small>(For lost focus after modified first input text so the <code>change</code> event will be triggered.)</small>
</p>
<p>
<button id="submit" type="submit">
Submit
</button>
<button id="button" type="button">
Trigger JS to set input value.
</button>
</p>
<p>Press F12 to view results in your browser console.</p>
</form>
Please press F12 to open browser's console and see result there.
Each time a user inputs some value, do something.
var element = document.getElementById('input');
element.addEventListener('input', function() {
// Do something
});
Keydown, keyup, input are events that fire immediately when input changes,
I would use keydown or input events to get the changed value from the input box.
const myObject = document.getElementById('Your_element_id');
myObject.addEventListener('keydown', function (evt) {
// your code goes here
console.log(myObject.value);
});
If you would like to monitor the changes each time there is a keystroke on the keyboard.
const textarea = document.querySelector(`#string`)
textarea.addEventListener("keydown", (e) =>{
console.log('test')
})
instead of id use title to identify your element and write the code as below.
$(document).ready(()=>{
$("input[title='MyObject']").change(()=>{
console.log("Field has been changed...")
})
});
I have a text input. It has a change and an input listener. In the input listener, I delete the value of the input, if it is "delete". The change listener simply alerts "Changed.".
Current behaviour:
There is no "Changed." alert when I type "delete" and stop editing, because the comparison base is changed as well.
Desired behaviour:
I want to see the "Changed." alert based on the value at the start of the editing, ignoring all the programatic changes made during the modification.
What is the simplest way of doing this?
Playgorund:
Click the input.
Delete the content.
Type "delete".
See how the text is deleted.
Click somewhere else.
See how the "Changed." alert is not displayed.
var input = document.querySelector('input');
input.addEventListener('change', function() {
alert('Changed.');
});
input.addEventListener('input', function() {
input.value = input.value.replace(/^delete$/, '');
});
<input value="example" />
My current solution is to add an attribute that I store the initial value in on each focus event, and compare it to the current value at the time of the blur event.
var input = document.querySelector('input');
input.addEventListener('focus', function() {
this.setAttribute('data-value-on-focus', this.value);
});
input.addEventListener('blur', function() {
if (this.getAttribute('data-value-on-focus') !== this.value) alert('Changed.');
});
input.addEventListener('input', function() {
this.value = this.value.replace(/^delete$/, '');
});
<input value="example" />
I'm trying to alert a value using jquery when it is generated from a javascript code, the value is generated on the input box the problem is jquery cannot detect the changes, commands i tested are "change, input" but when i manually input a value jquery triggers
sample code:
value is dynamically generated on the javascript and pushed / inserted to the inputbox, the value is not manually generated
javascript:
document.getElementById("displayDID").value = DisplayName ;
html:
<input type="text" id="displayDID" />
jquery:
$('#displayDID').on("input" ,function() {
var work = $(this).val();
alert(work);
});
the value of the id="displayDID" changes but jquery cannot detect it after execution.
sample fiddle http://jsfiddle.net/SU7bU/1/
add trigger to it
$('#gen').on('click',function() {
$('#field').val('val').trigger("change");
});
$(document).on("change",'#field' ,function() {
var work = $(this).val();
alert(work);
});
http://jsfiddle.net/ytexj/
It is because you have added the script before input is ready.Due to which, event is not getting set on that element.write the code on document ready:
$(document).ready(function(){
$('#displayDID').on("input" ,function() {
var work = $(this).val();
alert(work);
});
})
or use event delegation:
$(document).on("input",'#displayDID' ,function() {
var work = $(this).val();
alert(work);
});
Ok I will propose you one answer and let's see if it solve your problem.
If you use keyup, and you insert 3350 value, you will display 4 alert, and I think you want to display only 1 alert.
$(document).ready(function() {
var interval;
$("#variazioneAnticipo").on("input", function() {
var variazioneAnticipo = $("#variazioneAnticipo").val();
clearInterval(interval);
interval = setTimeout(function(){ showValue(variazioneAnticipo) }, 1000);
});
});
function showValue(value) {
alert("ANTICIPO VARIATO: " + value);
}
<input id="variazioneAnticipo" class="rightAlligned form-control" style="width: 60%" type="number" step="0.01" min="0" value="3" />
I explain it, when you input anything into the input, will trigger a setTimeout in 1 sec, if you press another key under this time, we clear the timeOut and we triiger again, so you will only have 1 alert 1 sec after the last input insert.
I hope it helps you, and soyy for my english :D
I'm using a JavaScript library that occasionally changes the value of an input field. I want to detect when that happens.
Apparently, the change and input events are not triggered when the value of an input field is changed (at least not on Chrome).
To verify that, I have tried this (using jQuery):
<script>
$(function() {
$('#inp').on('change',function() { console.log('change event'); });
$('#inp').on('input',function() { console.log('input event'); });
$('#inp').val('hello');
});
</script>
<input type="text" id="inp">
Neither the change event nor the input event is triggered when I call .val('hello').
How can I detect the change? (Please remember that the code that changes the value is outside my control, so I cannot add a call to trigger() there.)
There is a work around, you can pool the value of textbox after regular intervals and trigger the event when it is changed.
Live Demo
$('#elementId').change(function(){
alert("changed");
});
var previousVal = "";
function InputChangeListener()
{
if($('#elementId').val() != previousVal)
{
previousVal = $('#elementId').val();
$('#elementId').change();
}
}
setInterval(InputChangeListener, 500);
$('#elementId').val(3);
Edit based on comments for many elements.
You can use array and monitor, 30 element wont be a performance concern
Live Demo
$('.someclass').change(function(){
alert("changed, id >> " + this.id);
});
var hashTablePrevElem=[];
$('.someclass').each(function(){
hashTablePrevElem[this.id] = this.value;
});
function InputChangeListener()
{
$('.someclass').each(function(){
if(hashTablePrevElem[this.id] != this.value)
{
hashTablePrevElem[this.id] = this.value;
$(this).change();
}
});
}
I have a form and a button.
I need that when I click on a textfield, and then click this particular button, the textbox which was clicked last will change its value to say "BUTTON HAS BEEN CLICKED".
Is there a way via JavaScript how I can know the last textbox which was clicked?
Many thanks in advance.
You need to store a reference to the text box when you click it. The easiest way to do that is to create a global variable for the reference. Then you would update the reference with the textbox's onclick event. Here is an example:
HTML:
<input id="myTextBox" type="text" onclick="updateCurText(this);">
<input type="button" value="click me" onclick="updateText();">
JavaScript:
var currentTextBox = '';
function updateCurText(ele) {
currentTextBox = ele.id;
}
function updateText() {
document.getElementById(currentTextBox).value = 'BUTTON HAS BEEN CLICKED';
}
Live example.
jsumners is correct, however I would probably recommend avoiding global variables, and if you're using something like jQuery you have encapsulate a lot of the logic in a single file:
$(function() {
var lastBox = false, formSelector = "form.myClass";
// Change events
$(formSelector + " input[type='text']").click(function() {
lastBox = this;
});
// Button click
$(formSelector + " button").click(function() {
if (lastBox)
$(lastBox).val("BUTTON HAS BEEN CLICKED");
});
});
live