We've recently rolled out ESLint 2025 features in our team and accumulated a good deal of experience. Sharing it here as a reference, hoping it helps others tackling similar challenges.

Core Concepts

Building on this foundation, we can further optimize:

import { useReducer, useCallback } from "react";

const initialState = { items: [], filter: "", sort: "date" };

function reducer(state, action) {
  switch (action.type) {
    case "SET_ITEMS":
      return { ...state, items: action.payload };
    case "SET_FILTER":
      return { ...state, filter: action.payload };
    case "ADD_ITEM":
      return { ...state, items: [...state.items, action.payload] };
    case "REMOVE_ITEM":
      return {
        ...state,
        items: state.items.filter((i) => i.id !== action.payload),
      };
    default:
      throw new Error(`Unknown: ${action.type}`);
  }
}

This pattern is very practical in large-scale projects and can significantly reduce maintenance costs.

Deep Dive

In a real project, the usage gets a bit more complex:

type UnwrapPromise<T> = T extends Promise<infer U> ? U : T

async function fetchUser(id: string) {
  const res = await fetch(`/api/users/${id}`)
  return res.json() as Promise<{ id: string; name: string; email: string }>
}

type User = UnwrapPromise<ReturnType<typeof fetchUser>>

// 类型安全的事件系统
interface EventMap {
  login: { userId: string; timestamp: number }
  logout: { userId: string }
}

class TypedEmitter<T extends Record<string, any>> {
  private handlers = new Map<keyof T, Set<Function>>()
  on<K extends keyof T>(event: K, handler: (payload: T[K]) => void) {
    if (!this.handlers.has(event)) this.handlers.set(event, new Set())
    this.handlers.get(event)!.add(handler)
  }
  emit<K extends keyof T>(event: K, payload: T[K]) {
    this.handlers.get(event)?.forEach(h => h(payload))
  }
}

This approach improves both the testability and scalability of the code.

Real-World Implementation

Here is a complete example:

const express = require("express");
const app = express();

app.use(express.json());

class AppError extends Error {
  constructor(status, message) {
    super(message);
    this.statusCode = status;
  }
}

const asyncHandler = (fn) => (req, res, next) =>
  Promise.resolve(fn(req, res, next)).catch(next);

app.get(
  "/api/users/:id",
  asyncHandler(async (req, res) => {
    const user = await User.findById(req.params.id);
    if (!user) throw new AppError(404, "用户不存在");
    res.json({ data: user });
  }),
);

Pay attention to edge-case handling—this is crucial in production environments.

Tuning Strategies

The key is to understand the core logic:

import { useReducer, useCallback } from "react";

const initialState = { items: [], filter: "", sort: "date" };

function reducer(state, action) {
  switch (action.type) {
    case "SET_ITEMS":
      return { ...state, items: action.payload };
    case "SET_FILTER":
      return { ...state, filter: action.payload };
    case "ADD_ITEM":
      return { ...state, items: [...state.items, action.payload] };
    case "REMOVE_ITEM":
      return {
        ...state,
        items: state.items.filter((i) => i.id !== action.payload),
      };
    default:
      throw new Error(`Unknown: ${action.type}`);
  }
}

Performance optimization must be tailored to specific scenarios—not every situation calls for aggressive optimization.

Summary

• Always verify compatibility before using in production
• In team collaboration, conventions and documentation matter more than the technology itself
• Stay up-to-date with community trends; technical solutions require continuous iteration