fix(plugin-legacy): add default value of targets

packages/plugin-legacy/README.md

@@ -38,11 +38,11 @@ npm add -D terser
 ### `targets`
 
 - **Type:** `string | string[] | { [key: string]: string }`
-- **Default:** `undefined`
+- **Default:** `'last 2 versions and not dead, > 0.3%, Firefox ESR'`
 
   If explicitly set, it's passed on to [`@babel/preset-env`](https://babeljs.io/docs/en/babel-preset-env#targets).
 
-  The query is also [Browserslist compatible](https://github.com/browserslist/browserslist). The value `'defaults'`, is what is recommended by Browserslist. See [Browserslist Best Practices](https://github.com/browserslist/browserslist#best-practices) for more details.
+  The query is also [Browserslist compatible](https://github.com/browserslist/browserslist). See [Browserslist Best Practices](https://github.com/browserslist/browserslist#best-practices) for more details.
 
 ### `polyfills`
 

packages/plugin-legacy/package.json

@@ -37,6 +37,7 @@
   "dependencies": {
     "@babel/core": "^7.20.5",
     "@babel/preset-env": "^7.20.2",
+    "browserslist": "^4.21.4",
     "core-js": "^3.26.1",
     "magic-string": "^0.27.0",
     "regenerator-runtime": "^0.13.11",

packages/plugin-legacy/src/index.ts

@@ -20,6 +20,7 @@ import type {
 } from 'rollup'
 import type { PluginItem as BabelPlugin } from '@babel/core'
 import colors from 'picocolors'
+import browserslist from 'browserslist'
 import type { Options } from './types'
 
 // lazy load babel since it's not used during dev
@@ -119,7 +120,10 @@ const _require = createRequire(import.meta.url)
 
 function viteLegacyPlugin(options: Options = {}): Plugin[] {
   let config: ResolvedConfig
-  const targets = options.targets
+  const targets =
+    browserslist() ||
+    options.targets ||
+    'last 2 versions and not dead, > 0.3%, Firefox ESR'
   const genLegacy = options.renderLegacyChunks !== false
   const genDynamicFallback = genLegacy