How do I remove event listener in this typical case

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First of all, have a look at the full code:

JavaScript

let turn='X';
let isover=false;
// changing the turn
const change=()=>{
    return turn==='X'?'O':'X';
}
// check win
const check=()=>{
    let boxtext=document.getElementsByClassName('btext');
    let  wins = [
        [0,1,2],[3,4,5],[6,7,8],[0,3,6],[1,4,7],[2,5,8],[0,4,8],[2,4,6]
    ]
    wins.forEach((e)=>{
        if((boxtext[e[0]].innerText === boxtext[e[1]].innerText)&& 
          (boxtext[e[1]].innerText === boxtext[e[2]].innerText)&& 
          (boxtext[e[0]].innerText !== '')){
            document.querySelector('.info').innerText = 
                     `'${boxtext[e[0]].innerText}'  WON`;
            isover=true;
            document.querySelector('.info').style.color= 'rgb(142, 2, 109)';
            document.querySelector('.info').style.fontWeight='bold';
            let boxes=document.getElementsByClassName('box');
            Array.from(boxes).forEach(element=>{
            let boxtext=element.querySelector('.btext');
            element.removeEventListener('click',play(boxtext))
            })
        }
    })
}
// logic
let boxes=document.getElementsByClassName('box');
Array.from(boxes).forEach(element=>{
    let boxtext=element.querySelector('.btext');
    element.addEventListener('click',()=>play(boxtext))
    document.querySelector('#reset').addEventListener('click',()=>{
        boxtext.innerText='';
        turn='X';
        isover=false;
        document.getElementsByClassName('info')[0].innerText= turn+"'s turn";
        document.querySelector('.info').style.color= 'black';
        document.querySelector('.info').style.fontWeight='100';
    })
})
function play(boxtext) {
    if (boxtext.innerText === '') {
        boxtext.innerText = turn;
        turn = change();
        check();
        if (!isover) {
            document.getElementsByClassName('info')[0].innerText = turn + "'s turn";
        }
    }
}

I want to remove an event listener in a typical case where it is connected to an outer scope.

What I have tried:

I somehow figured it out that 'removeEventListener dosen't work with anonymous function'.
For example:

JavaScript

let btn=document.querySelector('.btn');
    btn.addEventListener('click',play);
    btn.addEventListener('keypress',play);
    function play(e){
        console.log(e)
        sum(4,5)
    }
    function sum(a,b){
        console.log(a+b)
    }
    setTimeout(()=>{
        console.log('removed')
        btn.removeEventListener('keypress',play)
    },5000)

But I'm unable to make this thing happen in the above given code.

Posted 9-Oct-23 20:41pm

ZAID razvi

Updated 24-Oct-23 11:06am

Deeksha Shenoy

v2

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Richard Deeming · Answer 1 · 2023-10-10T23:50:00

Quote:

JavaScript

element.removeEventListener('click',play(boxtext))

Breaking that line down, you want to remove a listener for the click event on the specified element. The listener you want to remove is the function returned from the play(boxtext) call.

But your play function doesn't return a function, so there is no listener to remove.

The simpler option would be to use event delegation[^], and test the isover variable at the start of the handler. For example:

JavaScript

document.addEventListener("click", (e) => {
    if (isover) { return; }
    
    let box = e.target;
    if (!box.classList.contains("box")) { box = box.closest(".box"); }
    if (!box) { return; }
    
    const boxtext = box.querySelector(".btext");
    if (!boxtext) { return; }
    
    play(boxtext);
});

document.getElementById("reset").addEventListener("click", () => {
    turn = "X";
    isover = false;
    document.querySelectorAll(".btext").forEach(boxtext => boxtext.innerText = "");
    
    const info = document.querySelector(".info");
    info.innerText = `${turn}'s turn`;
    info.style.color= 'black';
    info.style.fontWeight='100';
});

const check = () => {
    const wins = [
        [0,1,2], [3,4,5], [6,7,8], [0,3,6], [1,4,7], [2,5,8], [0,4,8], [2,4,6]
    ];

    const boxtext = document.getElementsByClassName("btext");
    for (const win of wins) {
        const t0 = boxtext[win[0]].innerText;
        const t1 = boxtext[win[1]].innerText;
        const t2 = boxtext[win[2]].innerText;
        if (t0 !== "" && t0 === t1 && t0 === t2) {
            isOver = true;
            const info = document.querySelector(".info");
            info.innerText = `${t0} WON`;
            info.style.color = 'rgb(142, 2, 109)';
            info.style.fontWeight = 'bold';
            return;
        }
    }
};

Steve Raw · Answer 2 · 2023-10-21T16:52:00

When it comes to removing event listeners, I understand it to be a very strange aspect of JavaScript. When I need to remove an existing event listener, the most effective way to be sure that it's removed is to create a cloned node of the element that the event listener is assigned to. Remove the original target element from the DOM, and replace it with the cloned node. When you clone a node, every event listener associated with the element is entirely removed. This doesn't work well for removing just a single event listener. They're all removed.

How do I remove event listener in this typical case

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