Can Javascript use Eventlistener for a collection?

Gips1
May 9, 2023
174 views
2 votes
4 Answers

I’m trying to add an eventlistener for a button collection inside of a for loop, but I’m kind of lost because in following example the eventlistener only works for the last button in the collection, and my country in addCountry function is undefined. I would appreciate any kind of feedback or help.

I have tried to console.log(i) and obviously it is working as it should. And I have console.log('.add'[i]) and that is displaying the button element so I don’t understand how this works really.

let countries = ["Sweden", "Norway", "Denmark", ]

const main = document.getElementById("maincontent")
const cart = document.getElementById('cart')

for (i = 0; i < countries.length; i++) {

  addContent()

  document.querySelectorAll('.add')[i].addEventListener('click', addCountry)
}

function addContent() {
  main.innerHTML += `<div>
  <h1>${countries[i]}</h1>
  <div class="one hide">
      <p>Some text</p>
      <button class="add">Add</button>
  </div>
  </div>`
}

function addCountry() {
  cart.innerHTML = `<div>
<h1>${countries[i]}</h1>
<div class="one hide">
    <p>Some text</p>
    <button class="delete">Delete</button>
</div>
</div>`
}

<main id="maincontent">

</main>
<div id="cart">

</div>

Tags: javascript

Answers

You can’t use i in addCountry. It’s a global variable, not closed over the loop iteration.

You need to put a closure into the loop, and then pass i as an argument to addCountry().

let countries = ["Sweden", "Norway", "Denmark", ]

const main = document.getElementById("maincontent")
const cart = document.getElementById('cart')

for (let i = 0; i < countries.length; i++) {
  addContent(i)
  document.querySelectorAll('.add')[i].addEventListener('click', () => addCountry(i))
}

function addContent(i){
  main.innerHTML+=`<div>
  <h1>${countries[i]}</h1>
  <div class="one hide">
      <p>Some text</p>
      <button class="add">Add</button>
  </div>
  </div>`
}
function addCountry(i) {
  cart.innerHTML = `<div>
<h1>${countries[i]}</h1>
<div class="one hide">
    <p>Some text</p>
    <button class="delete">Delete</button>
</div>
</div>`
}

Using event delegation and data attributes you can avoid having to add multiple event handlers.

let countries = ["Sweden", "Norway", "Denmark", ]

const main = document.getElementById("maincontent")
const cart = document.getElementById('cart')

const html = countries.map(addContent);
main.innerHTML = html.join('');

main.addEventListener("click", function (e) {
  const btn = e.target.closest('[data-country]');
  if (!btn) return;
  const country = btn.dataset.country;
  addCountry(country);
});

cart.addEventListener("click", function (e) {
  const btn = e.target.closest('.delete');
  if (!btn) return;
  btn.closest(".wrapper").remove();
});


function addContent(country) {
  return `
  <div>
    <h1>${country}</h1>
    <div class="one hide">
      <p>Some text</p>
      <button class="add" data-country="${country}">Add</button>
    </div>
  </div>`;
}

function addCountry(country) {
  cart.innerHTML += `
  <div class="wrapper">
    <h1>${country}</h1>
    <div class="one hide">
      <p>Some text</p>
      <button class="delete">Delete</button>
    </div>
  </div>`;
}

<main id="maincontent"></main>
<div id="cart"></div>

- developer
- May 9, 2023 at 8:40 pm
- 0 votes
0
You are doing a small mistake at event binding. Update this line of the code:-
```
for (i = 0; i < countries.length; i++) {
  addContent();

   document.querySelectorAll('.add').forEach((item)=>{
     item.addEventListener('click', addCountry);
   });
}
```
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Here’s another approach it seems easy to understand but don’t hesitate if you have any question.

This solution avoid to always use innerHTML!

I don’t understand if you want to duplicate nodes or just create a document as specified and add a listener to it.
in the clickHandler() method you can easily do what you want…
Duplicate an Object, add the destination to a cart…

If you want to see the logs, click on "Full page" for the snippet.

Best regards.

let countries = ["Sweden", "Norway", "Denmark"];
    function addElements(){
        for(var i=0; i<countries.length; i++){
            constructElement(i)
        }
    }
    function constructElement(i){
        var newDiv = document.createElement("div");
        var newH1 = document.createElement("h1");
        var newTitle = document.createTextNode(countries[i]);
        var innerDiv = document.createElement("div");
        innerDiv.classList.add("inDiv");
        var paragraph = document.createElement("p");
        var btn = document.createElement("button");
        btn.setAttribute("value", i);
        btn.classList.add("inButton");
        var newText = document.createTextNode("Country n°" + (i+1) + " :");
        var buttonText = document.createTextNode(countries[i]);
        newDiv.appendChild(newH1);
        newH1.appendChild(newTitle);
        newDiv.appendChild(innerDiv)
        innerDiv.appendChild(paragraph);
        paragraph.appendChild(newText);
        innerDiv.appendChild(btn);
        btn.appendChild(buttonText)
        document.body.appendChild(newDiv);
        btn.addEventListener("click", clickEvent);
    }
    addElements();
    function clickEvent(event){
        console.log("button clicked value = " + this.value + ", country = " + this.textContent);
        // then you may add conditions related to the button value...
        if(this.value == 0){
            console.log("Do you live in " + countries[this.value] + "?");
        }else if(this.value == 1){
            console.log("Are you happy in " + countries[this.value] + "?");  
        }else if(this.value == 2){
            console.log("Are you really leaving " + countries[this.value] + "?");    
        }
    }

        html, body{
            font-family: sans-serif;
        }
        h1{
            font-size: 1.2em;
        }
        p{
            margin:0;
        }
        .inDiv{
            padding:10px;
            color:#009900;
            border:1px solid #000000;
            width:300px;
            font-weight:bold;
        }
        .inButton{
            padding:5px;
            color:#990000;
            width:100px;
        }

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