如下

// ==UserScript==
// @name         洛谷私信自动回复
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  洛谷私信自动回复
// @author       d0j1a_1701
// @match        https://*.luogu.com.cn/*
// @icon         https://www.google.com/s2/favicons?sz=64&domain=luogu.com.cn
// ==/UserScript==

const message = '[自动回复]你好，我现在有事不在，一会再和你联系。';

const usr = window._feInjection.currentUser

async function reply(uid){
	await fetch("https://www.luogu.com.cn/api/chat/new", {
		headers: [
			["content-type", "application/json"],
			["referer", "https://www.luogu.com.cn/"],
			["x-csrf-token", document.querySelector("meta[name=csrf-token]").content],
		],
		body: JSON.stringify({
			user: uid,
			content: message,
		}),
		method: "POST",
	});
}

(function() {
    'use strict';
    if (window.location.href.search("/chat") != -1) return;
    console.log(window._feInjection);
	const socket = new WebSocket("wss://ws.luogu.com.cn/ws");
	socket.onopen = () => socket.send(JSON.stringify({
		type: "join_channel",
		channel: "chat",
		channel_param: String(usr.uid),
		exclusive_key: null,
	}));
	socket.onmessage = (e) => {
		const u = JSON.parse(e.data);
		if (u._ws_type === "server_broadcast" && u.message instanceof Object && u.message.sender.uid !== usr.uid) {
			reply(u.message.sender.uid)
			console.log(`msg from ${u.message.sender.uid}`)
		}
	};
})();

window._feInjection.currentUser总是取到null

无论怎样修改脚本注入位置都无效

但在调试器中运行又正常