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How to disable the browser back button using javascript in a HTML page. Can we get any callback method trigerred on click of backbutton on browser

How to disable the browser back button using javascript in a HTML page. Can we get any callback method trigerred on click of backbutton on browser using Javascript and not using Jquery Mobile library.
Solution would be really appreciated. I tried with few solutions online, but nothing seemed to work.

You should never do that. https://www.irt.org/script/311.htm
By the way, you may just warn the user using window.onbeforeunload.
You can-not actually disable browser back button. And there is no event for capturing the back button click.
If it is really necessary you can do something like that:
(function (global) {
var _extra_hash = "!";
var noBack = function () {
global.location.href += "#";
global.setTimeout(function () {
global.location.href += _extra_hash;
}, 50);
};
global.onhashchange = function () {
if (global.location.hash !== _extra_hash) {
global.location.hash = _extra_hash;
}
};
global.onload = function () {
noBack();
// this is for disabling backspace on page except on input fields and textarea..
/*document.body.onkeydown = function (e) {
var elm = e.target.nodeName.toLowerCase();
if (e.which === 8 && (elm !== 'input' && elm !== 'textarea')) {
e.preventDefault();
}
// stopping event bubbling up the DOM tree..
e.stopPropagation();
};*/
}
})(window);
But the user can still kill the tab. Anyway, It is generally a bad idea overriding the default behavior of web browser.

Javascript: How to read a hand held barcode scanner best?

I'd like to be able to scan barcodes via a hand held scanner and handle the results with Javascript.
A barcode-scanner works almost like a keyboard. It outputs the scanned/translated (barcode->number) data raw (right?). Actually I just need to catch the output and proceed. But how?
Here's some pseudocode I'd like to make work:
$(document).on("scanButtonDown", "document", function(e) {
// get scanned content
var scannedProductId = this.getScannedContent();
// get product
var product = getProductById(scannedProductId);
// add productname to list
$("#product_list").append("<li>" + product.name + "</li>");
});
Any ideas (frameworks, plugins, snippets)?
Any barcode-scanner (hardware) recommendation?
I found this and this good questions but I'd like to get more information about the handling. Just to focus a textarea may be not enough in my case.

Your pseudo code won't work, because you don't have access to the scanner to catch events like scanButtonDown. Your only option is a HID scanner, which behaves exactly like a keyboard. To differentiate scanner input from keyboard input you have two options: Timer-based or prefix-based.
Timer-based
The scanner is likely to input characters much quicker than a user can (sensibly) with a keyboard. Calculate how quickly keystrokes are being received and buffer fast input into a variable to pass to your getProductsId function. #Vitall wrote a reusable jQuery solution for catching barcode scanner input, you would just need to catch the onbarcodescanned event.
Prefix-based
Most scanners can be configured to prefix all scanned data. You can use the prefix to start intercepting all input and once you've got your barcode you stop intercepting input.
Full disclosure: I work as a consultant to Socket Mobile, Inc. who make handheld scanners.

After a lot of research and testing, what worked the best for me was to capture input from a barcode scanner without focusing a form input. Listen to the keydown and textInput events.
The textInput event acts like a paste event. It has then entire barcode data. In my case I am looking for UPC barcodes. The e.preventDefault() prevents the barcode data from being inserted into a form input:
document.addEventListener('textInput', function (e){
if(e.data.length >= 6){
console.log('IR scan textInput', e.data);
e.preventDefault();
}
});
I have tested this on Android 4.4 and 7.0 with a CipherLab IR scanner.
Example for listening to the keydown event. In my case I am able to assume that as long as a form input is not focused, the user is scanning a barcode.
let UPC = '';
document.addEventListener("keydown", function(e) {
const textInput = e.key || String.fromCharCode(e.keyCode);
const targetName = e.target.localName;
let newUPC = '';
if (textInput && textInput.length === 1 && targetName !== 'input'){
newUPC = UPC+textInput;
if (newUPC.length >= 6) {
console.log('barcode scanned: ', newUPC);
}
}
});
Of course, rather than checking the length of the string to determine a scan, you can listen for the e.keyCode === 13 in the keydown event listener.
Not all IR scanners will trigger the textInput event. If your device does not, then you can check to see if it is emitting something similar with:
monitorEvents(document.body);
Found this monitoring trick here: How do you log all events fired by an element in jQuery?

I'm little late but I made this work around based in some answers here.
let code = "";
let reading = false;
document.addEventListener('keypress', e => {
//usually scanners throw an 'Enter' key at the end of read
if (e.keyCode === 13) {
if(code.length > 10) {
console.log(code);
/// code ready to use
code = "";
}
} else {
code += e.key; //while this is not an 'enter' it stores the every key
}
//run a timeout of 200ms at the first read and clear everything
if(!reading) {
reading = true;
setTimeout(() => {
code = "";
reading = false;
}, 200); //200 works fine for me but you can adjust it
}
});

A barcode-scanner works almost like a keyboard.
It depends on the model. Every one that I've used works exactly like a keyboard (at least as far as the computer is concerned)
It outputs the scanned/translated (barcode->number) data raw (right?).
It outputs keycodes.
$(document).on("scanButtonDown"
You probably want keypress, not scanButtonDown.
Look at the event object to determine the "key" that was pressed.
To determine when the entire code has been scanned, you might get an "end of data" key (possibly a space or a return) or you might have to just count how many characters are being input.

Here is working fine.
It's working when input has focus and input hasn't focus
on_scanner() // init function
function on_scanner() {
let is_event = false; // for check just one event declaration
let input = document.getElementById("scanner");
input.addEventListener("focus", function () {
if (!is_event) {
is_event = true;
input.addEventListener("keypress", function (e) {
setTimeout(function () {
if (e.keyCode == 13) {
scanner(input.value); // use value as you need
input.select();
}
}, 500)
})
}
});
document.addEventListener("keypress", function (e) {
if (e.target.tagName !== "INPUT") {
input.focus();
}
});
}
function scanner(value) {
if (value == '') return;
console.log(value)
}
HTML
<input type="text" id="scanner" placeholder="scanner">

Tried all the solutions, but not worked as expected. I found very easiest solution onscan.js I have application using angular 8.
Very simple and good implementation.
For angular 8, I followed steps:
1.npm install onscan.js --save
2.open angular.json, add one entry to script array as "node_modules/onscan.js/onscan.min.js"
3.In component class, implement interface AfterViewInit
declare var onscan:any;
ngAfterViewInit(): void {
//Put focus to textbox and press scanner button
onScan.attachTo(document, {
suffixKeyCodes: [13], // enter-key expected at the end of a scan
reactToPaste: true, // Compatibility to built-in scanners in paste-mode (as opposed to keyboard-mode)
onScan: function (sCode, iQty) { // Alternative to document.addEventListener('scan')
console.log('Scanned: ' + iQty + 'x ' + sCode);
},
});
}
Best thing is scanned text appears into focued textbox element
Hope this help.

I wanted to share this topic using React too, as I struggled a lot with it.
I think most of the barcode scanners, such as Hanz Herdel said, terminate with ENTER. In my case, I found easier to wrap the input in a form and catch the submission event, prevent default and retrieve the value of the input.
I preferred this type of approach so to handle any type of barcode length, instead to check the length of it.
Here's how I handled it in React:
import { useState } from "react";
export default function Modal() {
const [repairArticles, setRepairArticles] = useState([]);
function handleBarcodeInput(e) {
e.preventDefault();
const input = e.target.querySelector("input");
const value = input.value;
setRepairArticles((prev) => {
return (prev = [...prev, value]);
});
input.value = "";
}
return (
<div>
<form onSubmit={(e) => handleBarcodeInput(e)} >
<input id="barcode-input" />
<button type="submit" className="hidden" />
</form>
<div className="mt-3">
{repairArticles.map((el, index) => {
return <p key={index}>{el}</p>;
})}
</div>
</div>
)
}

This is an extension to the answer given by Hanz Herdel incase you are using one of the PosX scanners or any other scanner that are capable of adding a special symbol to the beginning of the characters. In this case, the tilde (~) symbol:
let barcode = "";
let reading = false;
document.addEventListener("keydown", e => {
//console.log(e.key);
if (e.key == 'Enter') {
if (barcode.length == 17) {
if (barcode.charAt(0) == '~') {
console.log(barcode);
barcode = "";
}
}
}
else {
if (e.key != 'Shift') {
barcode += e.key;
}
}
if (!reading) {
reading = true;
setTimeout( () => {
barcode = "";
reading = false;
}, 200);
}
}, true)
You can change the barcode length and the timeout speed to your liking but this worked perfect for me.

Vue 2 implementation (i think vuejs's syntax is similar to angular):
BarcodeScanner.vue component code is here:
<template>
<input type="hidden" name="_barcode" v-model="finalCode" />
</template>
<script>
export default {
props: {
onSuccess: {
type: Function,
required: true
},
minLength: {
type: Number,
default: () => 10
}
},
data() {
return {
code: "",
finalCode: "",
fromScanner: false,
reading: false
};
},
mounted() {
document.addEventListener("keypress", this.documentKeyboardListener);
},
destroyed() {
document.removeEventListener("keypress", this.documentKeyboardListener);
},
methods: {
documentKeyboardListener(e) {
if (e.target.nodeName !== 'BODY') return;
if (e.code === "Enter") {
if (this.reading && this.code.length > this.minLength) {
if (this.onSuccess)
this.onSuccess(this.code);
this.finalCode = this.code;
this.code = "";
this.fromScanner = true;
}
} else {
this.code += e.key; //while this is not an 'enter' it stores the every key
}
//run a timeout of 200ms at the first read and clear everything
if (!this.reading) {
this.reading = true;
setTimeout(() => {
this.code = "";
this.reading = false;
this.fromScanner = false;
}, 200); //200 works fine for me but you can adjust it
}
},
},
};
</script>
You can invoke the component anywhere:
...
<barcode-scanner onSuccess="yourListener"/>
...
(Js scanner code is taken from Hanz Herdel)

I've just started working on a plugin that handles barcode scanning and credit card scanning (built on jQuery):
https://github.com/ericuldall/jquery-pos
Simple implementation:
$(function(){
$(document).pos();
$(document).on('scan.pos.barcode', function(event){
var barcode = event.code;
//handle your code here....
});
});
So far this plugin is only tested with one type of scanner and codes containing only digits, but if you have further requirements that aren't working with it, I'd be happy to adapt it to your needs. Please check out the github page and give it a whirl. Contributions are encouraged.
E

var txt = "";
function selectBarcode() {
if (txt != $("#focus").val()) {
setTimeout('use_rfid()', 1000);
txt = $("#focus").val();
}
$("#focus").select();
setTimeout('selectBarcode()', 1000);
}
$(document).ready(function () {
setTimeout(selectBarcode(),1000);
});
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<input type="text" name="tag" id="focus" placeholder="Use handheld RFID scanner">

Needs hardening but this routine, which counts on scanned data being sent in under 100ms, is working in production. Thanks to #jfbloom22 and other answers for inspiration and reminding me of monitorEvents.
It appears scanners need to be set to send "HID Keyboard"-type data(?) and be set to terminate with "Enter".
Although is purely JavaScript logic, was written in TypeScript app for a PCF (Power Apps Component Framework) project that allows the app to accept scan data without the need to focus on an input box. Globals were used as a convenience.
public Scan(evt: Event): void {
const e:KeyboardEvent = evt as KeyboardEvent;
const timeDiff = e.timeStamp - CheckInPCF.LastTimeStamp;
CheckInPCF.LastTimeStamp = e.timeStamp; //"global"
//console.log(e.key + ': ' + timeDiff);
if (timeDiff < 100) {
if (e.key == 'Enter') {
//Assemble complete scan text
CheckInPCF.ScanText = CheckInPCF.FirstCharacterCandidate + CheckInPCF.ScanText; //.replace('\u000D','');
//console.log('finished: ' + CheckInPCF.ScanText);
CheckInPCF._this._notifyOutputChanged(); //Power Apps related
}
else {
CheckInPCF.ScanText += e.key;
}
}
else {
CheckInPCF.ScanText = '';
CheckInPCF.FirstCharacterCandidate = e.key;
}
}

This code works fine for me, you can try it
var barcode = '';
var interval;
document.addEventListener('keydown', function(evt) {
if (evt.code === 'F12'){
evt.preventDefault();
}
if (interval){
clearInterval(interval);
}
if (evt.code == 'Enter') {
if (barcode){
$('#barcode').val(barcode);
console.log(barcode);
}
barcode = '';
return;
}
if (evt.key != 'Shift'){
barcode += evt.key;
}
interval = setInterval(() => barcode = '', 20);
});

Preventing ckeditor to display character on keypress

I have a CKEditor 3.0 instance 'editor' and on its 'key' event a listener is attached so that when that function is returning false it should not type that key character on editor, that is if key 'k' is pressed it should not be displayed on the editor if the function is returning false
editor.on('key', function(e)
{
alert(""+e.data.keyCode);
return false;
});
I used above code for this but it is not working, means the character is getting typed on the editor
Trying the same using a plugin where on keypress of keycode 65 the other language character should show up instead of english language character.
CKEDITOR.plugins.add( 'typing',
{
init: function( editor )
{
editor.addCommand( 'insertcharacter',
{
exec : function( editor )
{
alert(editor.id);
alert(editor.name);
editor.on('key', function(e)
{
alert("Hello"+e.data.keyCode);
if(e.data.keyCode == 65)
{
editor.insertText('Other Language Character');
}
return false;
});
}
});
can u suggest me any solution for this.
Thanks

found the answer recently. this worked for me in the latest version(4.x).
editor.document.on('keypress', function(e) {
e.data.preventDefault(); // this will prevent the default action for any event
//your code goes here
});

In v4 you can use editor.on('key') and cancel() the event when the appropriate key is pressed.
So to ignore k keypresses,
editor.on('key', function(evt) {
var keyCodeToIgnore = 'K'.charCodeAt(); // Upper case K. Only one k key.
var pressedKeyCode = evt.data.keyCode;
if ( pressedKeyCode === keyCodeToIgnore ) {
evt.cancel();
}
}
(That wouldn't prevent 'k's being added by other means, of course, such as pasting.)
See http://docs.ckeditor.com/#!/api/CKEDITOR.editor-event-key
You can also configure the editor to block specified keystrokes. Using that you can specify case. So to ignore k and not K:
config.blockedKeystrokes = [75]; // To ignore k and K: [75, 107]
Though you'd probably want to keep the default blockedKeystrokes as well.
See http://docs.ckeditor.com/#!/api/CKEDITOR.config-cfg-blockedKeystrokes
The first method lets you do other stuff of course. You could drive people crazy by ignoring a 'u' if the previous keypress was a 'q', for example.

use following code before return from function to Cancel/block the character/event.
e.cancelBubble = true;
e.returnValue = false;
e.cancel();
e.stop();
return false;
where e is in parameter of function

I came looking for a way to bind something to the the enter key press. Except I'm using contenteditable div tags, and maybe that made the above solutions not work for me.
However I came to this, that seems to be working perfectly
$(function () {
CKEDITOR.instances['<the DOM ID of your element>'].on('key', function (e) {
if (e.data.keyCode === 13) {
//yeet
e.cancel();
}
});
});

How to continue event propagation after cancelling?

When a user clicks a certain link I would like to present them with a confirmation dialog. If they click "Yes" I would like to continue the original navigation. One catch: my confirmation dialog is implemented by returning a jQuery.Deferred object which is resolved only when/if the user clicks the Yes button. So basically the confirmation dialog is asynchronous.
So basically I want something like this:
$('a.my-link').click(function(e) {
e.preventDefault(); e.stopPropogation();
MyApp.confirm("Are you sure you want to navigate away?")
.done(function() {
//continue propogation of e
})
})
Of course I could set a flag and re-trigger click but that is messy as heck. Any natural way of doing this?

Below are the bits from the code that actually worked in Chrome 13, to my surprise.
function handler (evt ) {
var t = evt.target;
...
setTimeout( function() {
t.dispatchEvent( evt )
}, 1000);
return false;
}
This is not very cross-browser, and maybe will be fixed in future, because it feels like security risk, imho.
And i don't know what happens, if you cancel event propagation.

It could be risky but seems to work at the time of writing at least, we're using it in production.
This is ES6 and React, I have tested and found it working for the below browsers. One bonus is if there is an exception (had a couple during the way making this), it goes to the link like a normal <a> link, but it won't be SPA then ofc.
Desktop:
Chrome v.76.0.3809.132
Safari v.12.1.2
Firefox Quantum v.69.0.1
Edge 18
Edge 17
IE11
Mobile/Tablet:
Android v.8 Samsung Internet
Android v.8 Chrome
Android v.9 Chrome
iOs11.4 Safari
iOs12.1 Safari
.
import 'mdn-polyfills/MouseEvent'; // for IE11
import React, { Component } from 'react';
import { Link } from 'react-router-dom';
class ProductListLink extends Component {
constructor(props) {
super(props);
this.realClick = true;
this.onProductClick = this.onProductClick.bind(this);
}
onProductClick = (e) => {
const { target, nativeEvent } = e;
const clonedNativeEvent = new MouseEvent('click', nativeEvent);
if (!this.realClick) {
this.realClick = true;
return;
}
e.preventDefault();
e.stopPropagation();
// #todo what you want before the link is acted on here
this.realClick = false;
target.dispatchEvent(clonedNativeEvent);
};
render() {
<Link
onClick={(e => this.onProductClick(e))}
>
Lorem
</Link>
}
}

I solved problem by this way on one of my projects. This example works with some basic event handling like clicks etc. Handler for confirmation must be first handler bound.
// This example assumes clickFunction is first event handled.
//
// you have to preserve called function handler to ignore it
// when you continue calling.
//
// store it in object to preserve function reference
var ignoredHandler = {
fn: false
};
// function which will continues processing
var go = function(e, el){
// process href
var href = $(el).attr('href');
if (href) {
window.location = href;
}
// process events
var events = $(el).data('events');
for (prop in events) {
if (events.hasOwnProperty(prop)) {
var event = events[prop];
$.each(event, function(idx, handler){
// do not run for clickFunction
if (ignoredHandler.fn != handler.handler) {
handler.handler.call(el, e);
}
});
}
}
}
// click handler
var clickFunction = function(e){
e.preventDefault();
e.stopImmediatePropagation();
MyApp.confirm("Are you sure you want to navigate away?")
.done(go.apply(this, e));
};
// preserve ignored handler
ignoredHandler.fn = clickFunction;
$('.confirmable').click(clickFunction);
// a little bit longer but it works :)

If I am understanding the problem correctly, I think you can just update the event to be the original event in that closure you have there. So just set e = e.originalEvent in the .done function.
https://jsfiddle.net/oyetxu54/
MyApp.confirm("confirmation?")
.done(function(){ e = e.originalEvent;})
here is a fiddle with a different example (keep the console open so you can see the messages):
this worked for me in chrome and firefox

I solved this by:
placing a event listener on a parent element
removing the class from the link ONLY when the user confirms
reclicking the link after I have removed the class.
function async() {
var dfd = $.Deferred();
// simulate async
setTimeout(function () {
if (confirm('Stackoverflow FTW')) {
dfd.resolve();
} else {
dfd.reject();
}
}, 0);
return dfd.promise();
};
$('.container').on('click', '.another-page', function (e) {
e.stopPropagation();
e.preventDefault();
async().done(function () {
$(e.currentTarget).removeClass('another-page').click();
});
});
$('body').on('click', function (e) {
alert('navigating somewhere else woot!')
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div class="container">
Somewhere else
</div>
The reason I added the event listener to the parent and not the link itself is because the jQuery's on event will bind to the element until told otherwise. So even though the element does not have the class another-page it still has the event listener attached thus you have to take advantage of event delegation to solve this problem.
GOTCHAS this is very state based. i.e. if you need to ask the user EVERYTIME they click on a link you'll have to add a 2nd listener to readd the another-page class back on to the link. i.e.:
$('body').on('click', function (e) {
$(e.currentTarget).addClass('another-page');
});
side note you could also remove the event listener on container if the user accepts, if you do this make sure you use namespace events because there might be other listeners on container you might inadvertently remove. see https://api.jquery.com/event.namespace/ for more details.

We have a similar requirement in our project and this works for me. Tested in chrome and IE11.
$('a.my-link').click(function(e) {
e.preventDefault();
if (do_something === true) {
e.stopPropogation();
MyApp.confirm("Are you sure you want to navigate away?")
.done(function() {
do_something = false;
// this allows user to navigate
$(e.target).click();
})
}
})

I edited your code. New features that I added:
Added namespace to event;
After click on element event will be removed by namespace;
Finally, after finish needed actions in "MyApp" section continue propagation by triggering others element "click" events.
Code:
$('a.my-link').on("click.myEvent", function(e) {
var $that = $(this);
$that.off("click.myEvent");
e.preventDefault();
e.stopImmediatePropagation();
MyApp.confirm("Are you sure you want to navigate away?")
.done(function() {
//continue propogation of e
$that.trigger("click");
});
});

This is untested but might serve as a workaround for you
$('a.my-link').click(function(e) {
e.preventDefault(); e.stopPropogation();
MyApp.confirm("Are you sure you want to navigate away?")
.done(function() {
//continue propogation of e
$(this).unbind('click').click()
})
})

Javascript IFrame/designmode and onkeydown event question

Apologize if this is answered already. Went through some of the related questions and google, but ultimately failed to see why this isn't working.
My code is as follows
<iframe id="editor"></iframe>
editorWindow = document.getElementById('editor').contentWindow;
isCtrlDown = false;
function loadEditor()
{
editorWindow.document.designMode = "on";
editorWindow.document.onkeyup = function(e) {
if (e.which == 91) isCtrlDown = false;
}
editorWindow.document.onkeydown = handleKeyDown;
}
function handleKeyDown(e)
{
if (e.which == 91) isCtrlDown = true;
if (e.which == 66 && isCtrlDown) editFont('bold');
if (e.which == 73 && isCtrlDown) editFont('italic');
}
function editFont(a,b)
{
editorWindow.document.execCommand(a,false,b);
editorWindow.focus();
}
This code works perfectly in Chrome, but the keyboard shortcuts do not work in Firefox. In fact, in Firefox it does not seem to register the events for keyup/keydown at all.
Am I doing something grossly wrong here that is mucking up Firefox?

For editable documents, you need to use addEventListener to attach key events rather than DOM0 event handler properties:
editorWindow.document.addEventListener("keydown", handleKeyDown, false);
If you care about IE 6-8, you will need to test for the existence addEventListener and add the attachEvent equivalent if it is missing.

Try using:
editorWindow = document.getElementById('editor').frameElement;
I'm not sure this will solve the issue, it may also be:
editorWindow = document.getElementById('editor').contentDocument;
Or even possibly:
editorWindow = document.getElementById('editor').frameElement.contentDocument;
One thing you can do is put the entire string in a try statement to catch any errors and see if the content is being grabbed from within the iframe.
try { editorWindow = document.getElementById('editor').contentWindow; } catch(e) { alert(e) };
The only other thought I have is that you're typing into a textbox which is within an iframe, and you may possibly have to add the onkeydown event to that specific item, such as:
var editorWindow = document.getElementById('editor').contentDocument;
var textbox = editorWindow.getElementById('my_textbox');
function loadEditor()
{
editorWindow.document.designMode = "on";
textbox.onkeydown = function(e) {
alert('hello there');
}
}
I hope one of these is the solution. I often find when it comes to cross-platform functionality it often boils down to a little trial and error.
Good Luck!