diff --git a/js/gulp/arrow-task.js b/js/gulp/arrow-task.js
index 2de20947dc2f5..ab3639e80a026 100644
--- a/js/gulp/arrow-task.js
+++ b/js/gulp/arrow-task.js
@@ -30,12 +30,12 @@ import { pipeline } from 'stream/promises';
 
 export const arrowTask = ((cache) => memoizeTask(cache, function copyMain(target) {
     const out = targetDir(target);
-    const dtsGlob = `${targetDir(`es2015`, `cjs`)}/**/*.ts`;
+    const dtsGlob = `${targetDir(`es2015`, `esm`)}/**/*.ts`;
     const cjsGlob = `${targetDir(`es2015`, `cjs`)}/**/*.js`;
     const esmGlob = `${targetDir(`es2015`, `esm`)}/**/*.js`;
     const es2015UmdGlob = `${targetDir(`es2015`, `umd`)}/*.js`;
     const esnextUmdGlob = `${targetDir(`esnext`, `umd`)}/*.js`;
-    const cjsSourceMapsGlob = `${targetDir(`es2015`, `cjs`)}/**/*.map`;
+    const cjsSourceMapsGlob = `${targetDir(`es2015`, `cjs`)}/**/*.js.map`;
     const esmSourceMapsGlob = `${targetDir(`es2015`, `esm`)}/**/*.map`;
     const es2015UmdSourceMapsGlob = `${targetDir(`es2015`, `umd`)}/*.map`;
     const esnextUmdSourceMapsGlob = `${targetDir(`esnext`, `umd`)}/*.map`;
@@ -43,10 +43,10 @@ export const arrowTask = ((cache) => memoizeTask(cache, function copyMain(target
         observableFromStreams(gulp.src(dtsGlob), gulp.dest(out)), // copy d.ts files
         observableFromStreams(gulp.src(cjsGlob), gulp.dest(out)), // copy es2015 cjs files
         observableFromStreams(gulp.src(cjsSourceMapsGlob), gulp.dest(out)), // copy es2015 cjs sourcemaps
-        observableFromStreams(gulp.src(esmSourceMapsGlob), gulp.dest(out)), // copy es2015 esm sourcemaps
+        observableFromStreams(gulp.src(esmSourceMapsGlob), gulpRename((p) => { p.basename = p.basename.replace('.js', '.mjs'); }), gulpReplace(`.js"`, `.mjs"`), gulp.dest(out)), // copy es2015 esm sourcemaps
         observableFromStreams(gulp.src(es2015UmdSourceMapsGlob), gulp.dest(out)), // copy es2015 umd sourcemap files, but don't rename
         observableFromStreams(gulp.src(esnextUmdSourceMapsGlob), gulp.dest(out)), // copy esnext umd sourcemap files, but don't rename
-        observableFromStreams(gulp.src(esmGlob), gulpRename((p) => { p.extname = '.mjs'; }), gulpReplace(`.js'`, `.mjs'`), gulp.dest(out)), // copy es2015 esm files and rename to `.mjs`
+        observableFromStreams(gulp.src(esmGlob), gulpRename((p) => { p.extname = '.mjs'; }), gulpReplace(`.js'`, `.mjs'`), gulpReplace(`.js.map`, `.mjs.map`), gulp.dest(out)), // copy es2015 esm files and rename to `.mjs`
         observableFromStreams(gulp.src(es2015UmdGlob), gulpRename((p) => { p.basename += `.es2015.min`; }), gulp.dest(out)), // copy es2015 umd files and add `.es2015.min`
         observableFromStreams(gulp.src(esnextUmdGlob), gulpRename((p) => { p.basename += `.esnext.min`; }), gulp.dest(out)), // copy esnext umd files and add `.esnext.min`
     ]).pipe(share({ connector: () => new ReplaySubject(), resetOnError: false, resetOnComplete: false, resetOnRefCountZero: false }));
diff --git a/js/gulp/package-task.js b/js/gulp/package-task.js
index 99eb705daeff4..8d061566a3648 100644
--- a/js/gulp/package-task.js
+++ b/js/gulp/package-task.js
@@ -129,7 +129,7 @@ const createScopedPackageJSON = (target, format) => (({ name, ...orig }) =>
             // set "module" if building scoped ESM target
             module:   format === 'esm' ? `${mainExport}.node.js` : undefined,
             // set "sideEffects" to false as a hint to Webpack that it's safe to tree-shake the ESM target
-            sideEffects: format === 'esm' ? sideEffects('mjs') : undefined,
+            sideEffects: format === 'esm' ? sideEffects('js') : undefined,
             // include "esm" settings for https://www.npmjs.com/package/esm if building scoped ESM target
             esm:      format === `esm` ? { mode: `auto`, sourceMap: true } : undefined,
             // set "types" (for TypeScript/VSCode)
diff --git a/js/gulp/typescript-task.js b/js/gulp/typescript-task.js
index 31769e3b1b236..ecc326b0f5aa0 100644
--- a/js/gulp/typescript-task.js
+++ b/js/gulp/typescript-task.js
@@ -61,10 +61,9 @@ function compileTypescript(out, tsconfigPath, tsconfigOverrides, writeSourcemaps
     );
     const writeSources = observableFromStreams(tsProject.src(), gulp.dest(path.join(out, 'src')));
     const writeDTypes = observableFromStreams(dts, sourcemaps.write('./', { includeContent: false, sourceRoot: './src' }), gulp.dest(out));
-    const mapFile = tsProject.options.module === tsc.ModuleKind.ES2015 ? esmMapFile : cjsMapFile;
     const writeJSArgs = writeSourcemaps ? [
         js,
-        sourcemaps.write('./', { mapFile, includeContent: false, sourceRoot: './src' }),
+        sourcemaps.write('./', { includeContent: false, sourceRoot: './src' }),
         gulp.dest(out)
       ] : [
         js,
@@ -73,6 +72,3 @@ function compileTypescript(out, tsconfigPath, tsconfigOverrides, writeSourcemaps
     const writeJS = observableFromStreams(...writeJSArgs);
     return ObservableForkJoin([writeSources, writeDTypes, writeJS]);
 }
-
-const cjsMapFile = (mapFilePath) => mapFilePath;
-const esmMapFile = (mapFilePath) => mapFilePath.replace('.js.map', '.mjs.map');