手写事件代理（委托）

[Sunny-117]

No description provided.

[JeromeD3]

function addEventListener(element, type, fn, selector) {
if (!selector) {
element.addEventListener(type, fn)
} else {
element.addEventListener(type, function (event) {
const target = event.target
if (target.matches(selector)) {
fn.call(target, event)
}
})
}
}

[kangkang123269]

function addEventListener(element, type, fn, selector) {
    // 检查元素、类型和回调函数是否存在
    if (!element || !type || !fn) {
        return;
    }

    // 如果没有选择器，则直接添加事件监听器
    if (!selector) {
        element.addEventListener(type, fn);
        return;
    }

    // 添加带有事件代理的监听器
    element.addEventListener(type, function (event) {
        let targets = Array.from(element.querySelectorAll(selector));
        
        if (targets.includes(event.target)) {
            fn.call(event.target, event);
        }
   });
}