Error: You must set either “output.file” for a single-file build or “output.dir” when generating multiple chunks

rollup报错：

Error: You must set either “output.file” for a single-file build or “output.dir” when generating multiple chunks

这个错误是output的file和dir配置问题，先看看下面三种配置就明白了。

第一种

代码：

import resolve from '@rollup/plugin-node-resolve';
import babel from '@rollup/plugin-babel';

export default {
  input: 'src/main.js',
  output: {
    file: 'bundle.js',
    format: 'iife',
  },
  plugins: [
    resolve(),
    babel({ babelHelpers: 'bundled' })
  ]
};

打包目录文件：bundle.js

第二种

代码：

import resolve from '@rollup/plugin-node-resolve';
import babel from '@rollup/plugin-babel';

export default {
  input: 'src/main.js',
  output: {
    format: 'iife',
    dir:'build'
  },
  plugins: [
    resolve(),
    babel({ babelHelpers: 'bundled' })
  ]
};

打包目录文件：build/main.js

第三种

代码：

import resolve from '@rollup/plugin-node-resolve';
import babel from '@rollup/plugin-babel';

export default {
  input: 'src/main.js',
  output: {
    file: 'build/bundle.js',
    format: 'iife',
  },
  plugins: [
    resolve(),
    babel({ babelHelpers: 'bundled' })
  ]
};

打包目录文件：build/bundle.js