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Removing event listeners before leaving a page

I've developed a javascript drag and drop that mostly uses the standard 'allowdrop', 'drag' and 'drop' events.
I wanted to customise the 'ghosted' dragged object, so I've added a display:none div that get populated with the innerHTML of the draggable element and made visible (display:block;) when the user starts dragging.
The draggable div is absolutely positioned and matches the mouse movements. For this I needed to add 3 event listeners to document.body. They are as follows:
document.body.addEventListener('dragover', function (ev) {
console.log("dragover event triggered");
ev = ev || window.event;
ev.preventDefault();
dragX = ev.pageX;
dragY = ev.pageY;
document.getElementById("dragged-container").style.left = (dragX - dragOffsetX) + "px";
document.getElementById("dragged-container").style.top = (dragY - dragOffsetY - 10) + "px";
if (mostRecentHoveredDropTargetId!="") {
if (dragX<mostRecentHoveredDropTargetRect.left || dragX>mostRecentHoveredDropTargetRect.right || dragY<mostRecentHoveredDropTargetRect.top || dragY>mostRecentHoveredDropTargetRect.bottom) {
document.getElementById(mostRecentHoveredDropTargetId).classList.remove("drop-target-hover");
mostRecentHoveredDropTargetId = "";
}
}
});
document.body.addEventListener('drop', function (ev) {
console.log("drop event triggered");
ev.preventDefault();
var data = ev.dataTransfer.getData("text"); // data set to the id of the draggable element
if (document.getElementById(data)!=null) {
document.getElementById(data).classList.remove("dragged");
document.getElementById("dragged-container").innerHTML = "";
document.getElementById("dragged-container").style.display = "none";
var draggablesClasses = document.getElementById(data).className;
if ((draggablesClasses.indexOf('draggable')==-1 || draggablesClasses=="") && document.getElementById(data).getAttribute('draggable')=="true") {
if (draggablesClasses=="") {
document.getElementById(data).className += "draggable";
} else {
document.getElementById(data).className += " draggable";
}
}
}
});
// resets dragged-container and origin .draggable, when mouse released outside browser window
document.body.addEventListener('mouseleave', function (ev) {
if (jqueryReady==true) {
$(".dragged").addClass("draggable");
$(".dragged").removeClass("dragged");
}
document.getElementById("dragged-container").innerHTML = "";
document.getElementById("dragged-container").style.display = "none";
});
This is all working fine. The drag and drop performs exactly as I expect.
The problem is when I go to another page, obviously those body event listeners are still running.
I've seen a number of answers here and have tried everything I've seen. For starters this:
window.onunload = function() {
console.log("about to clear event listeners prior to leaving page");
document.body.removeEventListener('dragover', null);
document.body.removeEventListener('drop', null);
document.body.removeEventListener('mouseleave', null);
return;
}
...but the console.log output doesn't even appear (let alone the 'null's being wrong, I'm pretty sure). I've also tried this, in the jQuery ready function:
$(window).bind('beforeunload', function(){
console.log("about to clear event listeners prior to leaving page");
document.body.removeEventListener('dragover', null);
document.body.removeEventListener('drop', null);
document.body.removeEventListener('mouseleave', null);
});
..but, once again, the console isn't even receiving that output.
I have also tried both the above with 'onbeforeunload' AND 'onunload'.
What am I doing wrong? - specifically to do with removing these window.body event listeners, I mean (Anything else I can sort out later).
Thanks.

removeEventListener requires the handler
Don't use anonymous functions is the solution.
Like this:
var dragHandler = function (ev) {
console.log("dragover event triggered");
};
document.body.addEventListener('dragover', dragHandler);
and after:
window.onunload = function() {
console.log("about to clear event listeners prior to leaving page");
document.body.removeEventListener('dragover', dragHandler);
return;
}

Jquery trigger on keypress

I am Using wordpress as cms
I have made a code which Runs a like() function when i press the left key
i try to trigger .love in like() Function
but it doesnt works
Here is my Code
var h2top = 0;
function like(){
scrollTop = jQuery(window).scrollTop();
jQuery('.container .post').each(function(i, h2){ /* loop through article headings */
h2top = jQuery(h2).offset().top ; /* get article heading top */
if (scrollTop<h2top-19) { /* compare if document is below heading */
alert("Ram");
jQuery(this).find('.love').trigger( "click" );
return false; /* exit function */
}
});
}
Here is the jquery code for Keypress events
jQuery(document).ready(function ($) {
$(document.documentElement).keyup(function (event) {
var direction = null;
// handle cursor keys
if (event.keyCode == 37) {
// go left
like();
$("#sad").closest('div').addClass('left');
alert("left");
} else if (event.keyCode == 39) {
// go right
alert("right");
}
});
});
Just using alert() to check whether the code is running or not

Just
$(document).keyup(function(e) {
alert (1);
// use event.which instead of keyCode
});
Instead of
$(document.documentElement).keyup(function (event) {
Other error, in your like function at the line jQuery(this).find('.love').trigger( "click" );
this is not the jQuery context, you must use $(this) like
jQuery($(this)).find('.love').trigger( "click" );
Example (updated)
http://jsbin.com/azUnUlO/1/

Adding keyboard shortcuts (up, down, enter) to search input suggestions div

I have a search suggestion div that appears when you keyUp an input. This works fine, but now I am trying to make keyboard shortcuts in action.
I want a behavior like when you click down keyboard arrow button a span gets selected and if it is selected then another span that is after gets selected, similarly, if you click up arrow an upward span gets selected, when you click enter then link opens.
I am stuck because I could not remove a:hover and could not add classes to it. Even after I have basically no idea how to do it. But I really tried hard and a lot..
Here is a jsfiddle link (type anything in field). maybe somebody will help me.

This code should go when the request is made and data is being returned:
<script type="text/javascript">
$(document).ready(function(){
total = 3;
$(".result-item").mouseenter(
function(){
hovered = $(this).attr("id");
total = 3;
$(".result-item").each(function(){
$(this).children("a").css({
'background-color':'#e4e4e4',
'color':'#000000'
});
$(this).find(".searchheading").css({
'color':'#191919'
});
$(this).find(".searchcaption").css({
'color':'#555555'
});
});
$(this).children("a").css({
'background-color':'#b7b7b7',
'color':'#ffffff'
});
$(this).find(".searchheading").css({
'color':'#ffffff'
});
$(this).find(".searchcaption").css({
'color':'#f1f1f1'
});
}
);
});
</script>
And this code on a page where request is made:
$("#suggestions").hide();
$("#search").bind('keyup', function(event){
if (event.which == 40 || event.which == 38 || event.which == 13) return false;
else
{
hovered = undefined;
lookup($(this).val());
}
});
$("#search").bind('keydown', 'down', function(evt){
if ($("#suggestions").is(":visible"))
{
if (typeof hovered == 'undefined')
{
$("#result-item-0").trigger("mouseenter");
return;
}
count = parseInt($("#"+hovered).attr("count"));
next = (count + 1);
if (next == total)
next = 0;
$("#result-item-"+next).trigger("mouseenter");
}
});
$("#search").bind('keydown', 'up', function(evt){
if ($("#suggestions").is(":visible"))
{
if (typeof hovered == 'undefined')
{
$("#result-item-"+(total-1)).trigger("mouseenter");
return;
}
count = parseInt($("#"+hovered).attr("count"));
prev = (count - 1);
if (prev == -1)
prev = (total-1);
$("#result-item-"+prev).trigger("mouseenter");
}
});
$("#search").bind('keydown', 'return', function(evt){
if ($("#suggestions").is(":visible"))
{
if (typeof hovered == 'undefined')
{
str = $("#search").val();
window.location.href = urlencode(str); // urlencode is a custom function
return false;
}
count = parseInt($("#"+hovered).attr("count"));
current = count;
$("#result-item-"+current).trigger("mouseenter");
$("#suggestions").fadeOut();
window.location.href = $("#"+hovered).children("a").attr("href");
}
});
})
;
Also I removed onkeyup="" attribute on element, this approach is nicer.

Fabric.js right mouse click

Is there a way to receive right click mouse events on a Fabric.js canvas?
The following code works only with left click:
canvas.observe('mouse:down', function(){console.log('mouse down'));

NOTE: Most answers above are outdated; this answer applies to the latest Fabric version 2.7.0
Simply enable firing right/middle click events for your Fabric canvas
The config for firing right click and middle click events in the canvas can be found here for fireRightClick and here for fireMiddleClick and are set to false by default. This means right and middle click events are by default disabled.
The parameter stopContextMenu for stopping context menu to show up on the canvas when right clicking can be found here
You can enable these simply by setting the values when creating your canvas:
var canvas = new fabric.Canvas('canvas', {
height: height,
width: width,
fireRightClick: true, // <-- enable firing of right click events
fireMiddleClick: true, // <-- enable firing of middle click events
stopContextMenu: true, // <-- prevent context menu from showing
});
Now your mousedown event will fire for all clicks and you can distinguish them by using the button identifier on the event:
For canvas:
canvas.on('mouse:down', (event) => {
if(event.button === 1) {
console.log("left click");
}
if(event.button === 2) {
console.log("middle click");
}
if(event.button === 3) {
console.log("right click");
}
}
For objects:
object.on('mousedown', (event) => {
if(event.button === 1) {
console.log("left click");
}
if(event.button === 2) {
console.log("middle click");
}
if(event.button === 3) {
console.log("right click");
}
}
When clicking on objects you can reach the "real" mouse dom event through event.e:
if(event.button === 3){
console.log(event.e);
}

I've implemented right click by extending the fabric.Canvas class. Take a look here the _onMouseDown method.
Basically the right mouse down event for an object was disabled in fabricjs by default.

If you want to handle right clicks (on canvas or its objects), then set context menu listener on upper-canvas element. Using canvas method findTarget you can check if any target was clicked and if so, you can check type of the target.
let scope = this;
jQuery(".upper-canvas").on('contextmenu', function (options: any) {
let target: any = scope.canvas.findTarget(options, false);
if (target) {
let type: string = target.type;
if (type === "group") {
console.log('right click on group');
} else {
scope.canvas.setActiveObject(target);
console.log('right click on target, type: ' + type);
}
} else {
scope.canvas.discardActiveObject();
scope.canvas.discardActiveGroup();
scope.canvas.renderAll();
console.log('right click on canvas');
}
options.preventDefault();
});

The way I did this was to listen for a right click event across the entire canvas and match up the x,y coordinates of the click event to the object which is currently sitting at the given location. This solution feels a little like a hack but hey, it works!
$('#my_canvas').bind('contextmenu', function (env) {
var x = env.offsetX;
var y = env.offsetY;
$.each (canvas._objects, function(i, e) {
// e.left and e.top are the middle of the object use some "math" to find the outer edges
var d = e.width / 2;
var h = e.height / 2;
if (x >= (e.left - d) && x <= (e.left+d)) {
if(y >= (e.top - h) && y <= (e.top+h)) {
console.log("clicked canvas obj #"+i);
//TODO show custom menu at x, y
return false; //in case the icons are stacked only take action on one.
}
}
});
return false; //stops the event propigation
});

Here's what I did, which makes use of some built-in fabric object detection code:
$('.upper-canvas').bind('contextmenu', function (e) {
var objectFound = false;
var clickPoint = new fabric.Point(e.offsetX, e.offsetY);
e.preventDefault();
canvas.forEachObject(function (obj) {
if (!objectFound && obj.containsPoint(clickPoint)) {
objectFound = true;
//TODO: whatever you want with the object
}
});
});

Using arrow keys with jQuery scrollTo

I have successfully implemented the scrollTo jQuery plugin which scrolls to the next div with the class "new" when a link is clicked. However, I would also like to be able to use the arrow keys to scroll up and down to the next/previous divs of the same class.
I have looked all over the internet but have been unable to find out how to do this. I am very new to JS so very simple instructions would be appreciated!
Here is the relevant code:
<script type="text/javascript">
jQuery(function($){
$('<div id="next_arrow"></div>')
.prependTo("body") //append the Next arrow div to the bottom of the document
.click(function(){
scrollTop = $(window).scrollTop();
$('.new').each(function(i, h2){ // loop through article headings
h2top = $(h2).offset().top; // get article heading top
if (scrollTop < h2top) { // compare if document is below heading
$.scrollTo(h2, 800); // scroll to in .8 of a second
return false; // exit function
}
});
});
});
</script>
What do I need to add to this to make the arrow keys work?
Thanks,
Ted

You can use the keydown event listener to listen for keypresses. You can use this on <input> fields and the like. Because keydown events bubble up the DOM, you can use it on the document object to catch any keypress on the page:
$(function () {
$(document).keydown(function (evt) {
alert("Key pressed: " + evt.keyCode);
});
});
Each keypress has a code. If you use the code above in your web page, you'll see that the key code for the down arrow is 40. You can solo this out using an if or switch statement in the handler:
jQuery(function () {
$(document).keydown(function (evt) {
if (evt.keyCode == 40) { // down arrow
alert("You pressed down.");
}
});
});
Now you need to bind in the code that actually jumps to the next heading. I recommend abstracting the code out into a function so you can use it for both keypresses and clicks. Here is the function, together with a variant of your original code that uses it:
// Here is the function:
function scrollToNew () {
scrollTop = $(window).scrollTop();
$('.new').each(function(i, h2){ // loop through article headings
h2top = $(h2).offset().top; // get article heading top
if (scrollTop < h2top) { // compare if document is below heading
$.scrollTo(h2, 800); // scroll to in .8 of a second
return false; // exit function
}
});
}
// Here is your original code, modified to use the function:
jQuery(function () {
$("#next").click(scrollToNew);
});
Finally, you can add in the keypress code and call the function from there:
function scrollToNew () {
scrollTop = $(window).scrollTop();
$('.new').each(function(i, h2){ // loop through article headings
h2top = $(h2).offset().top; // get article heading top
if (scrollTop < h2top) { // compare if document is below heading
$.scrollTo(h2, 800); // scroll to in .8 of a second
return false; // exit function
}
});
}
jQuery(function () {
$("#next").click(scrollToNew);
$(document).keydown(function (evt) {
if (evt.keyCode == 40) { // down arrow
evt.preventDefault(); // prevents the usual scrolling behaviour
scrollToNew(); // scroll to the next new heading instead
}
});
});
Update: To scroll upwards, do two things. Change the keydown handler to:
$(document).keydown(function (evt) {
if (evt.keyCode == 40) { // down arrow
evt.preventDefault(); // prevents the usual scrolling behaviour
scrollToNew(); // scroll to the next new heading instead
} else if (evt.keyCode == 38) { // up arrow
evt.preventDefault();
scrollToLast();
}
}
and write a scrollToLast() function based off of scrollToNew() that finds the last new heading that isn't on the page:
function scrollToLast () {
scrollTop = $(window).scrollTop();
var scrollToThis = null;
// Find the last element with class 'new' that isn't on-screen:
$('.new').each(function(i, h2) {
h2top = $(h2).offset().top;
if (scrollTop > h2top) {
// This one's not on-screen - make a note and keep going:
scrollToThis = h2;
} else {
// This one's on-screen - the last one is the one we want:
return false;
}
});
// If we found an element in the loop above, scroll to it:
if(scrollToThis != null) {
$.scrollTo(scrollToThis, 800);
}
}

Just for giving more idea, working with arrays.
var panel_arr = new Array();
$(document).ready(function(e) {
$('.parallax-panel-wrapper').each(function(i, element){
panel_arr.push( $(this).attr("id") );
});
var current_parallax_panel_no = 0;
$(document).keydown(function (evt) {
if (evt.keyCode == 40) { // down arrow
evt.preventDefault(); // prevents the usual scrolling behaviour
if(current_parallax_panel_no < (panel_arr.length-1)) current_parallax_panel_no++;
scrollByArrowKeys(1);
} else if (evt.keyCode == 38) { // up arrow
evt.preventDefault(); // prevents the usual scrolling behaviour
if(current_parallax_panel_no >= 1) current_parallax_panel_no--;
scrollByArrowKeys(0);
}
});
function scrollByArrowKeys(add_more){
scrollToThis = (($("#" + panel_arr[current_parallax_panel_no]).offset().top) + add_more ; // get element top
$.scrollTo(scrollToThis, 800);
}
});

You need to capture the keypress event and decide which keycode was pressed
$(document).keypress(function(e) {
switch(e.keyCode) {
case 37:
//left arrow pressed
break;
case 39:
//right arrow pressed
break;
}
});