class ListenDomChange {
    constructor(dom, callbackDomChange) {
        //   监听 dom 节点
        this.dom = dom;
        //   回调函数
        this.callbackDomChange = callbackDomChange;
    }
    // 监听 dom变化
    mutationListen() {
        // 选择需要观察变动的节点
        const targetNode = this.dom

        // 观察器的配置（需要观察什么变动）
        const config = { attributes: true, childList: true, subtree: true };

        // 当观察到变动时执行的回调函数
        const callback = function (mutationsList, observer) {
            // Use traditional 'for loops' for IE 11
            for (let mutation of mutationsList) {
                if (mutation.type === "childList") {
                    console.log("A child node has been added or removed.");
                } else if (mutation.type === "attributes") {
                    console.log("The " + mutation.attributeName + " attribute was modified.");
                }
            }
        };

        // 创建一个观察器实例并传入回调函数
        const observer = new MutationObserver(callback);

        // 以上述配置开始观察目标节点
        observer.observe(targetNode, config);

        // 之后，可停止观察
        observer.disconnect();
    }

    getPerformance() {
        // Time to when activation occurred
        let activationStart =
            performance.getEntriesByType("navigation")[0].activationStart;

        // Time to first paint
        let firstPaint = performance.getEntriesByName("first-paint")[0].startTime;

        // Time to first contentful paint
        let firstContentfulPaint = performance.getEntriesByName(
            "first-contentful-paint",
        )[0].startTime;

        console.log("time to first paint: " + (firstPaint - activationStart));
        console.log(
            "time to first-contentful-paint: " + (firstContentfulPaint - activationStart),
        );
    }
}

export {
    ListenDomChange
}