npm install -g rollup

import path from "path";
console.log("hello rollop", path.join("", "hello"));

rollup -i index.js --file dist.js --format umd

export const funA = () => {
  console.log("a");
};
export const funB = () => {
  console.log("b");
};

import { funA } from "./a";
funA();
console.log("hello rollup");

rollup -i index.js --file dist.js --format es

const funA = () => {
  console.log("a");
};
funA();
console.log("hello rollop");

import path from "path";
import { funA } from "./a";
funA();
console.log("hello rollop", path.join(__dirname, "/hello"));
export const x = 12;

export const funA = () => {
  console.log("a");
};
export const funB = () => {
  console.log("b");
};

rollup [options] <entry file>  选项 输入文件
--help 帮助文档
-v, --version 查看版本
-i, --input <filename> 输入单个文件
-f, --format <format> 输出格式
-o, --file <output>  输出单个文件
-d, --dir <dirname>  输出多个文件
-w, --watch 监听文件改变，并重新打包
-c, --config <filename> 指定配置文件使用
--environment <values>  指定环境变量

rollup -i index.js -i a.js --dir dist

rollup -i index.js --format iife
index.js → stdout...
Creating a browser bundle that depends on "path". You might need to include https://github.com/snowpackjs/rollup-plugin-polyfill-node
var index = (function (exports, path) {
  'use strict';
  function _interopDefaultLegacy (e) { return e && typeof e === 'object' && 'default' in e ? e : { 'default': e }; }
  var path__default = /*#__PURE__*/_interopDefaultLegacy(path);
  const funA = () => {
    console.log("a");
  };
  funA();
  console.log("hello rollop", path__default["default"].join(__dirname, "/hello"));
  const x = 12;
  exports.x = x;
  Object.defineProperty(exports, '__esModule', { value: true });
  return exports;
})({}, path);

rollup -i index.js --format cjs
index.js → stdout...
'use strict';
Object.defineProperty(exports, '__esModule', { value: true });
var path = require('path');
function _interopDefaultLegacy (e) { return e && typeof e === 'object' && 'default' in e ? e : { 'default': e }; }
var path__default = /*#__PURE__*/_interopDefaultLegacy(path);
const funA = () => {
  console.log("a");
};
funA();
console.log("hello rollop", path__default["default"].join(__dirname, "/hello"));
const x = 12;
exports.x = x;

rollup -i index.js --format es
index.js → stdout...
import path from 'path';
const funA = () => {
  console.log("a");
};
funA();
console.log("hello rollop", path.join(__dirname, "/hello"));
const x = 12;
export { x };

rollup -i index.js --format umd --name index
index.js → stdout...
(function (global, factory) {
  typeof exports === 'object' && typeof module !== 'undefined' ? factory(exports, require('path')) :
  typeof define === 'function' && define.amd ? define(['exports', 'path'], factory) :
  (global = typeof globalThis !== 'undefined' ? globalThis : global || self, factory(global.index = {}, global.path));
})(this, (function (exports, path) { 'use strict';
  function _interopDefaultLegacy (e) { return e && typeof e === 'object' && 'default' in e ? e : { 'default': e }; }
  var path__default = /*#__PURE__*/_interopDefaultLegacy(path);
  const funA = () => {
    console.log("a");
  };
  funA();
  console.log("hello rollop", path__default["default"].join(__dirname, "/hello"));
  const x = 12;
  exports.x = x;
  Object.defineProperty(exports, '__esModule', { value: true });
}));

 rollup -i index.js --file dist.js --format umd --name index

export default {
  input: "index.js",
  output: {
    file: "dist.js",
    format: "umd",
    name: "index",
  },
};

rollup --config rollup.config.js

// rollup.config.js
console.log(process.env.MODE);
const mode = process.env.MODE;
const isLocal = mode === "local";
export default {
  input: "index.js",
  output: {
    file: "dist.js",
    format: isLocal ? "es" : "umd",
    name: "index",
  },
};

rollup --config rollup.config.js --environment MODE:local

import path from "path";
import { funA } from "./a";
import pkg from "./package.json";
console.log(pkg);
funA();
console.log("hello rollop", path.join(__dirname, "/hello"));
export const x = 12;

npm install @rollup/plugin-json --save-dev 
npm install rollup

./node_modules/.bin/rollup --config rollup.config.js --plugin json