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addEventListener getting ignored

I have a loop that adds elements to a dropdown.
The elements get added, and I want to add an event that happens when the user clicks on one of the elements.
So I am adding an event listener like this.
for (var i = 0; cities.length > i; i++) {
if (cities[i].toLowerCase().indexOf(value.toLowerCase()) !== -1 && citiesList <= 10) {
citiesList ++;
dropdown.classList.add('show');
dropdown.innerHTML += '<a class="dropdown-item" id="dropdown_item-' + i + '" href="#">' + cities[i] + '</a>';
var item = document.getElementById('dropdown_item-' + i);
item.addEventListener("click", function(){ console.log("test") });
console.log(item);
}
}
But when I click on the elements the event does not fire even though console.log logs the item correctly and when I add the listener manually through the console it works. I tried using a timeout function but to no prevail.

When you += with the innerHTML of a container, the container's contents get completely re-parsed from their HTML markup alone. Anything else (such as event listeners not in the HTML markup) will be lost. Use insertAdjacentHTML instead:
The insertAdjacentHTML() method of the Element interface parses the specified text as HTML or XML and inserts the resulting nodes into the DOM tree at a specified position. It does not reparse the element it is being used on, and thus it does not corrupt the existing elements inside that element. This avoids the extra step of serialization, making it much faster than direct innerHTML manipulation.
dropdown.insertAdjacentHTML('beforeend', '<a class="dropdown-item" id="dropdown_item-' + i + '" href="#">' + cities[i] + '</a>');
That said, it looks like you may be giving the element an ID just so that you can select it and subsequently attach a listener to it. Dynamic IDs are a pretty bad idea - if the reason for the ID, it would be better to create the element using createElement instead:
const a = document.createElement('a');
a.className = "dropdown-item";
a.textContent = cities[i];
a.addEventListener("click", function() {
console.log("test")
});
dropdown.appendChild(a);
Keep in mind that i will equal to cities.length after the end of the loop, given your current code. If you reference i inside the listener callback, if you want it to reference the i used for that particular iteration, you need a block-scoped i instead: change
for (var i = 0; cities.length > i; i++) {
to
for (let i = 0; cities.length > i; i++) {
(or, even better, use Array.prototype.forEach or something like that instead of manually messing with indicies)

Why my Chrome extension event doesn't work?

I'm trying to create a chrome extension. I had a problem with the affectation of event for the new element that i append to the dom of site with content. Js
If I add an event to an element' 'for example class' exist already in the page, it works correctly. Just for my new appended element((in the code iadded a button ,the event is just an alert to test))
function tst() {
myclass = $("._3hg-._42ft");
myclass = myclass.not(".supp");
myclass.addClass("supp");
var patt = /https:\/\/(.)*\.facebook\.com\/(.)*\/(posts|photos|videos)\/(\w|\.|\d)*/g;
for (i = 0; i < myclass.length; i++) {
result = patt.exec(myclass[i]);
myclass.append('<button class="fact" id=' + result[0] + ' style="position: absolute;">fact</button>');
};
/* this is a simple event*/
/***********************/
$(".fact").on('click', function() {
alert("no event work ");
});

Making somewhat broad assumption here in my answer that it is JavaScript/jQuery related and is NOT an extension...or is so still in that context.
You need to attach the event to the container here perhaps for the dynamically created elements. Lots of global stuff, suggested to not do that, updated there.
Appends a lot of buttons perhaps? might need to only hit DOM once but left as-is in this isolated function.
function tst() {
let myclass = $("._3hg-._42ft")
.not(".supp");
myclass.addClass("supp");
//let result = {};
var patt = /https:\/\/(.)*\.facebook\.com\/(.)*\/(posts|photos|videos)\/(\w|\.|\d)*/g;
var i = 0; //avoid global
for (i; i < myclass.length; i++) {
// broad assumption of the returned value from patt.exec() here
// not even sure why it needs an id, have a class, use for css
let result = patt.exec(myclass[i]);
myclass.append('<button class="fact" id="' + result[0] + '">fact</button>');
}
/* attache event to pre-existing element */
/***********************/
myclass.on('click', ".fact", function() {
alert("event works");
});
}
button.fact {
position: absolute;
}

Using this within functions called with onclick event in Javascript

I'm currently building a small Todo list application using vanilla Javascript but I'm having some issues creating a delete button that onClick removes it's parent element.
From what I have read, when an onClick is called in Javascript the this keyword can be used to refer to the element that called the function. With this in mind I have the following code:
window.onload = initialiseTodo;
function addRecord(){
var title = document.getElementById('issueTitle');
var issueContent = document.getElementById('issueContent');
var contentArea = document.getElementById('contentArea');
if(title.value.length > 0 && issueContent.value.length > 0){
var newItem = document.createElement('div');
newItem.id = 'task' + count++;
newItem.className = 'task';
newItem.innerHTML = '<div class="taskbody"><h1>' + title.value + '</h1>'+ issueContent.value + '</div><div class="deleteContainer">'
+ '<a class="delete">DELETE</a></div>';
contentArea.appendChild(newItem);
assignDeleteOnclick();
}
}
function deleteRecord(){
this.parentNode.parentNode.parentNode.parentNode.removeChild(this.parentNode.parentNode);
}
function assignDeleteOnclick(){
var deleteArray = document.getElementsByClassName('delete');
for(var i=0;i<deleteArray.length;i++){
deleteArray[i].onclick= deleteRecord();
}
}
function initialiseTodo(){
var btn_addRecord = document.getElementById('addRecord');
btn_addRecord.onclick = addRecord;
}
Basically I have a form that has two fields. When these fields are filled and the addRecord button is clicked a new div is added at the bottom of the page. This div contains a delete button. After the creation of this I assign an onclick event to the delete button which assigns the deleteRecord function when the delete button is clicked. My issue is with the deleteRecord function. I have used this to refer to the calling element (the delete button) and wish to remove the task div that is the outermost container however I current get a message that says: 'Cannot read property 'parentNode' of undefined ' which suggests to me the this keyword is not working correctly.
Any help would be greatly appreciated.
I've added the full code to a fiddle.
http://jsfiddle.net/jezzipin/Bd8AR/
J

You need to provide the element itself as a parameter. I did so by changing the html to include onclick="deleteRecord(this)" to make it a little easier to deal with. This means you can remove the assignDeleteOnclick() function
function deleteRecord(elem){
elem.parentNode.parentNode.remove();
}
Demo
You might style the .content to be hidden better if there are no elements to prevent that extra white space
Edit
Since you don't want an inline onclick, you can do it with js the same:
function deleteRecord(elem){
elem.parentNode.parentNode.remove();
}
function assignDeleteOnclick(){
var deleteArray = document.getElementsByClassName('delete');
for(var i=0;i<deleteArray.length;i++){
// Has to be enveloped in a function() { } or else context is lost
deleteArray[i].onclick=function() { deleteRecord(this); }
}
}
Demo

Javascript addEventListener inside a loop

I'm trying to add an event listener to some elements which I generate in the loop. I must use div.lastChild - although in this example it's pretty stupid. But that's just demonstration:
<div id="someArea">
</div>
<script type="text/javascript">
var func = function() {
alert('Callback works');
}
var func1 = function() {
alert('Test');
}
var func2 = function() {
alert('Test2');
}
var div = document.getElementById("someArea");
var callbacks = [func, func1, func2];
for(var i = 0; i <= 2; i++) {
div.innerHTML += '<input type="button" value="' + i + '" />';
(function(i) {
console.log(div.lastChild);
div.lastChild.addEventListener('click', callbacks[i], false);
}(i));
}
</script>
The event works only for the last button. What am I missing here?

Why it's not working.
When you do this...
div.innerHTML += '<input type="button" value="' + i + '" />';
...in every iteration of the loop you're destroying the old DOM nodes inside div (and therefore their handlers), and recreating new nodes (but no handlers). The destruction includes the input elements that were added in previous iterations.
That's why only the last one works, since after that point, you've assigned the handler to the last element, but the other ones are brand new and untouched.
A solution.
Instead of treating the DOM as though it was a string of HTML markup, consider using DOM methods for element creation...
for(var i = 0; i <= 2; i++) {
var input = document.createElement('input');
input.type = 'button';
input.value = i;
input.addEventListener('click', callbacks[i], false);
div.appendChild(input);
}
Notice that I removed the immediately invoked function. For your code, it was unnecessary since i is being evaluated in the loop instead of later in the handler.
The DOM is not HTML, but .innerHTML makes you think it is.
It's important to understand innerHTML. When working with the DOM, there is no HTML markup. So when you get the .innerHTML, the DOM is being analyzed, and a new HTML string is created.
When you assign to .innerHTML, you're destroying all the current content, and replacing it with new nodes created from the HTML string.
So when you do...
div.innerHTML += '<input...>'
...you're first creating the new HTML string from the current content, then concatenating the new HTML content to the string, then destroying the old nodes and creating new ones from the new string.
This is terribly inefficient, and as you've already seen, it destroys any data associated with the original elements, including handlers.

Javascript - Dynamically assign onclick event in the loop

I have very simple html page with js code:
<html>
<head>
<title></title>
</head>
<body>
<div id="divButtons">
</div>
<script type="text/javascript">
var arrOptions = new Array();
for (var i = 0; i < 10; i++) {
arrOptions[i] = "option" + i;
}
for (var i = 0; i < arrOptions.length; i++) {
var btnShow = document.createElement("input");
btnShow.setAttribute("type", "button");
btnShow.value = "Show Me Option";
var optionPar = arrOptions[i];
btnShow.onclick = function() {
showParam(optionPar);
}
document.getElementById('divButtons').appendChild(btnShow);
}
function showParam(value) {
alert(value);
}
</script>
</body>
</html>
That page binds 10 buttons, but when you click on any button it always shows alert "option9". How is it possible assign onclick event to show correspondent option !?
Thanks!

You'll have to do something like this:
btnShow.onclick = (function(opt) {
return function() {
showParam(opt);
};
})(arrOptions[i]);

Consider the fact that when the onclick() function is executed, all it has is:
showParam(optionPar);
, verbatim. The optionPar will be resolve at the time the click event is executed, and at this point it most likely be the latest value you assigned to it. You should generally avoid passing variables in such a way.
The problem you are trying to solve is best solved by re-writing the piece such as:
btnShow.value = "Show Me Option";
var optionPar = arrOptions[i];
btnShow.optionPar = optionPar;
btnShow.onclick = function(e) {
// if I'm not mistaking on how to reference the source of the event.
// and if it would work in all the browsers. But that's the idea.
showParam(e.source.optionPar);
}

The accepted answer seems to work, but seems to be confusing and a somewhat cumbersome way to do it. A better way perhaps might be to use the data attribute for the element you're looking to assign the event listener for. It's simple, easy to understand, and way less code. Here's an example:
btnShow.data = arrOptions[i];
btnShow.onclick = function() {
showParam(this.data);
}

I attach an event handler:
window.onload = function() {
var folderElement;
tagFolders = document.getElementById("folders");
for (i = 0; i < folders.length; i++) {
folderElement = folderButtons[i];
folderElement = document.createElement("button");
folderElement.setAttribute("id", folders[i]);
folderElement.setAttribute("type", "button");
folderElement.innerHTML = folders[i];
if (typeof window.addEventListener !== "undefined") {
folderElement.addEventListener("click", getFolderElement, false);
} else {
folderElement.attachEvent("onclick", getFolderElement);
}
tagFolders.appendChild(folderElement);
}
which can retrieve anything from the element that triggered the event:
// This function is the event handler for the folder buttons.
function getFolderElement(event) {
var eventElement = event.currentTarget;
updateFolderContent(eventElement.id);
}
in which case you have to embed the option inside the element / tag. In my case I use the id.

For jquery, check out the adding event data section from the API:
...
for (var i = 0; i < arrOptions.length; i++) {
$('<input id="btn" type="button" value="Show Me Option"><input>').appendTo("#divButtons")
$('#btn').bind("click", {
iCount: i},
function(event) {
showParam(arrOptions[iCount]);
});
}

The accepted answer is correct but I feel that no real explanation was done.
Let me try to explain, the issue here is classical missing closure.
The variable 'i' is getting increased by 1 per loop iteration,
and the on-click event actually is not being executed, whether only applied to the a element, it getting summarize up to the length of arrOptions which is 10.
So, the loop continues up until 'i' is 10,
Then, whenever the on-click event is being triggered, it takes the value of i which is 10.
now, for the solution,
in the solution we are using a closure, so that when we apply the value of 'i' to the on-click event of the a element, it actually gets the exact value of i at in time.
The inner function of the onclick event create a closure where it references the parameter (arrOptions[i]), meaning what the actual i variable is at the right time.
The function eventually closes with that value safely,
and can then return its corresponding value when the on-click event is being executed.

You pass just the reference of the variable to the function, not it's value. So every time the loop is iterated, it assigns a reference to your anonymous function and all of them point to the same value in memory. But since you use the same variable name in the loop, you overwrite the value of the variable. You can concatenate the variable to a string to preserve it's value. For example like that:
btnShow.onclick = new Function("", "showParam(" + arrOptions[i] + ");");
The first parameter is the name of the function but afaik it is optional (it can be left blank or omitted at all).

pp();
function pp()
{
for(j=0;j<=11;j++)
{
if(j%4==0)
{
html+= "<br>";
}
html += "<span class='remote' onclick='setLift(this)' >"+ j+"</span>";
}
document.getElementById('el').innerHTML = html;
}
function setLift(x)
{
alert(x.innerHTML);
}