如何将JS对象从服务器端传递到NodeJS中的客户端

// 服务器端
const obj = { key: 'value' };
const jsonString = JSON.stringify(obj);
res.send(jsonString);

// 客户端
fetch('/api/endpoint')
  .then(response => response.json())
  .then(obj => {
    console.log(obj);
  });

// 服务器端
const express = require('express');
const app = express();

app.get('/api/endpoint', (req, res) => {
  const obj = { key: 'value' };
  res.json(obj);
});

// 客户端
fetch('/api/endpoint')
  .then(response => response.json())
  .then(obj => {
    console.log(obj);
  });

// 服务器端
const WebSocket = require('ws');
const wss = new WebSocket.Server({ port: 8080 });

wss.on('connection', ws => {
  const obj = { key: 'value' };
  ws.send(JSON.stringify(obj));
});

// 客户端
const ws = new WebSocket('ws://localhost:8080');

ws.addEventListener('message', event => {
  const obj = JSON.parse(event.data);
  console.log(obj);
});

// 服务器端
exports.main_handler = async (event, context, callback) => {
  const obj = { key: 'value' };
  return {
    statusCode: 200,
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify(obj)
  };
};

// 客户端
fetch('/api/endpoint')
  .then(response => response.json())
  .then(obj => {
    console.log(obj);
  });