Implement flatMap fallback for better Node.js compatibility

[danburzo]

The flatMap Array method has only been introduced in Node 11, but Node 10 will be still around until (at least) 2021. I propose a simple fallback for the missing method, to make the loader compatible with more Node.js versions:

diff --git a/src/minify-plugin.js b/src/minify-plugin.js
index 7916f1e..1e8e83f 100644
--- a/src/minify-plugin.js
+++ b/src/minify-plugin.js
@@ -3,6 +3,8 @@ const { RawSource, SourceMapSource } = require('webpack-sources')
 const isJsFile = /\.js$/i
 const pluginName = 'esbuild-minify'
 
+const flatMap = (arr, cb) => arr.flatMap ? arr.flatMap(cb) : [].concat(...arr.map(cb))
+
 class ESBuildMinifyPlugin {
   constructor(options) {
     this.options = { ...options }
@@ -39,7 +41,7 @@ class ESBuildMinifyPlugin {
       compilation.hooks.optimizeChunkAssets.tapPromise(
         pluginName,
         async (chunks) => {
-          const transforms = chunks.flatMap((chunk) => {
+          const transforms = flatMap(chunks, (chunk) => {
             return chunk.files
               .filter((file) => isJsFile.test(file))
               .map(async (file) => {

If there's interest in this, I can make a PR.

[privatenumber]

Good call. Thanks for catching!

PRs welcome!

[github-actions]

🎉 This issue has been resolved in version 2.1.1 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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