chore: modify package.json and rollup.config

Author: ssi02014

package.json

@@ -7,7 +7,7 @@
     "commit-amend-build": "scripts/commit-amend-build.sh",
     "prebuild": "rimraf dist/**",
     "dev": "cross-env NODE_ENV=development BABEL_ENV=rollup rollup -w -c -o dist/purify.js",
-    "build": "cross-env NODE_ENV=production rollup -c",
+    "build": "rollup -c",
     "build:umd": "rollup -c -f umd -o dist/purify.js",
     "build:umd:min": "rollup -c -f umd -o dist/purify.min.js -p terser",
     "build:es": "rollup -c -f es -o dist/purify.es.js",

rollup.config.js

@@ -6,7 +6,7 @@ const { terser } = require('rollup-plugin-terser');
 const pkg = require('./package.json');
 
 const env = process.env.NODE_ENV;
-const isProd = env === 'production';
+const event = process.env.npm_lifecycle_event; // build, build:umd, ...
 const version = process.env.npm_package_version;
 const license = fs
   .readFileSync('./src/license_header', 'utf8')
@@ -32,7 +32,7 @@ const config = {
       ...commonOutputConfig,
       file: pkg.production,
       format: 'umd',
-      plugins: isProd ? [terser()] : [],
+      plugins: event === 'build' ? [terser()] : [],
     },
     {
       ...commonOutputConfig,