无法通过EventListener删除removeEventListener

Question

我正在尝试删除EventListener，但是在Chrome调试模式下显示的错误消息如下：

未定义的TypeError:无法读取未定义的属性“removeEventListener”

我不知道问题出在哪里，密码如下：

​

window.addEventListener("load", init, false);
var vote = null;
function init() {
    vote = document.querySelectorAll("div>span>img");


    for (var index = 0; index < vote.length; index++) {
        //document.getElementById(("img" + index)).innerHTML = '<img   src="../images/voteoff.png" />';
        event.stopPropagation();
        vote[index].setAttribute("src", "../images/voteoff.png");
        vote[index].setAttribute("id", index);




        vote[index].addEventListener("mouseover", handleMouseOver, false);
        vote[index].addEventListener("mouseout", handleMouseOut, false);
        vote[index].addEventListener("click", MouseOnclickVote, false);
        //vote[index].onmouseover = function () { MouseOverVote(this.id);}
        //vote[index].onmouseout = MouseOutVote;
        event.stopPropagation();
        //vote[index].onclick = function () { MouseOnclickVote(this.id); }

    }

函数MouseOnclickVote() {

        length = this.id;
        console.debug(length);
        for (var index = 0; index <= length ;  index++) {
            console.debug(index);
            console.debug(vote[index]);
            vote[index].removeEventListener("mouseout", handleMouseOver);
            vote[index].removeEventListener("mouseover", handleMouseOut);

        }


    }
}
var handleMouseOver = function MouseOverVote() {


    length = this.id;



    for (var index = 0; index <= length ; index++) {

        vote[index].setAttribute("src", "../images/voteok.png");
        vote[index].parentNode.parentNode.nextSibling.nextSibling.firstChild.textContent = "你按了" + (index + 1) + "個讚";
        event.stopPropagation();
    }
}

var handleMouseOut = function MouseOutVote() {

    for (var index = 0; index < vote.length ; index++) {
        vote[index].setAttribute("src", "../images/voteoff.png");
        vote[index].parentNode.parentNode.nextSibling.nextSibling.firstChild.textContent = "";
        event.stopPropagation();
    }
}

</script>

​

Answer 1

看来你的投票应该是投票索引

但是，您也可以先检查删除事件侦听器是否是一个函数。

if(typeof vote[index].removeEventListener === "function") {
  // you can remove it 
} else { // you can't remove it, it doesn't have a listener
}