dom 加载监听事件 及解析

document.addEventListener("DOMContentLoaded", function (_event) {
    console.log("初始DOM 加载并解析");
});
window.addEventListener("load", function (_event) {
    console.log("window 所有资源加载完成");
});

document.addEventListener('readystatechange', function (_event) {
    console.log(document.readyState);
    if (document.readyState === "complete") {
        console.log('初始DOM,加载解析完成')
    }
});

window.addEventListener("beforeunload", function (event) {
    console.log('即将关闭')
    event.returnValue = "o/";
});
window.addEventListener('unload', function (_event) {
    console.log('即将关闭1');
});