diff --git a/.eslintrc.js b/.eslintrc.js
index 0abe6e88cb9b..0dc9da6b1ac0 100644
--- a/.eslintrc.js
+++ b/.eslintrc.js
@@ -45,7 +45,6 @@ module.exports = {
   "overrides": [{
       "files": [
         "devtools/**",
-        "js/**",
         "layout/**",
         "media/**",
         "memory/**",
diff --git a/.prettierignore b/.prettierignore
index a2ece3a753bf..76b1ca17b6fd 100644
--- a/.prettierignore
+++ b/.prettierignore
@@ -40,7 +40,6 @@ toolkit/components/telemetry/datareporting-prefs.js
 toolkit/components/telemetry/healthreport-prefs.js
 
 # Ignore all top-level directories for now.
-js/**
 layout/**
 media/**
 memory/**
@@ -108,6 +107,10 @@ dom/security/test/sri/script*
 dom/base/test/file_bug687859-charset.js
 dom/base/test/file_bug687859-inherit.js
 
+# Ignore preprocessed files.
+js/src/builtin/**/*.js
+js/src/shell/**/*.js
+
 # Ignore devtools debugger files
 # Keep in sync with devtools/client/debugger/.prettierignore
 devtools/client/debugger/src/workers/parser/tests/fixtures/functionNames.js