diff --git a/.circleci/config.yml b/.circleci/config.yml
index 6b1e671ea..91b7230b2 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -41,6 +41,19 @@ jobs:
       - checkout
       - install-dependencies
       - build-site
+      - persist_to_workspace:
+          root: "."
+          paths:
+            - "_site"
+
+  test:
+    docker:
+      - image: circleci/ruby:2.6-node-browsers
+    steps:
+      - checkout
+      - install-dependencies
+      - attach_workspace:
+          at: "."
       - run:
           name: run tests
           command: bundle exec rspec spec
@@ -54,11 +67,13 @@ jobs:
   accessibility:
     docker:
       - image: circleci/ruby:2.6-node-browsers
+    environment:
+      SKIP_BUILD: true
     steps:
       - checkout
       - install-dependencies
-      # It's not necessary to build the site prior to running end-to-end tests, as it's done as a
-      # pre-step of the npm test script.
+      - attach_workspace:
+          at: "."
       - run:
           name: run end-to-end tests
           command: npm test
@@ -83,6 +98,18 @@ jobs:
           name: check optimized images
           command: make lint-assets
 
+  check-javascript-syntax:
+    docker:
+      - image: circleci/ruby:2.6-node-browsers
+    steps:
+      - checkout
+      - install-dependencies
+      - attach_workspace:
+          at: "."
+      - run:
+          name: check es5 syntax
+          command: npm run es5-safe
+
   # Running external links as a separate job so we don't fail the build directly
   # but do get the feedback/info
   test-external-links:
@@ -91,7 +118,8 @@ jobs:
     steps:
       - checkout
       - install-dependencies
-      - build-site
+      - attach_workspace:
+          at: "."
       - run:
           name: Run htmlproofer (external links only)
           command: make htmlproofer_external
@@ -107,11 +135,24 @@ workflows:
       - build
       - eslint
       - check-optimized-assets
-      - test-external-links
-      - accessibility
+      - test:
+          requires:
+            - build
+      - check-javascript-syntax:
+          requires:
+            - build
+      - test-external-links:
+          requires:
+            - build
+      - accessibility:
+          requires:
+            - build
   daily-external-link-checker:
     jobs:
-      - test-external-links
+      - build
+      - test-external-links:
+          requires:
+            - build
     triggers:
       - schedule:
           # Once a day at 12pm
diff --git a/package-lock.json b/package-lock.json
index ebb3248f5..94e97fb90 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -20,6 +20,7 @@
       },
       "devDependencies": {
         "@axe-core/puppeteer": "^4.1.0",
+        "acorn": "^8.1.0",
         "eslint": "^7.15.0",
         "eslint-plugin-prettier": "^3.2.0",
         "get-port": "^5.1.1",
@@ -2484,9 +2485,9 @@
       "dev": true
     },
     "node_modules/acorn": {
-      "version": "8.0.4",
-      "resolved": "https://registry.npmjs.org/acorn/-/acorn-8.0.4.tgz",
-      "integrity": "sha512-XNP0PqF1XD19ZlLKvB7cMmnZswW4C/03pRHgirB30uSJTaS3A3V1/P4sS3HPvFmjoriPCJQs+JDSbm4bL1TxGQ==",
+      "version": "8.1.0",
+      "resolved": "https://registry.npmjs.org/acorn/-/acorn-8.1.0.tgz",
+      "integrity": "sha512-LWCF/Wn0nfHOmJ9rzQApGnxnvgfROzGilS8936rqN/lfcYkY9MYZzdMqN+2NJ4SlTc+m5HiSa+kNfDtI64dwUA==",
       "bin": {
         "acorn": "bin/acorn"
       },
@@ -4462,8 +4463,7 @@
         "esprima": "^4.0.1",
         "estraverse": "^4.2.0",
         "esutils": "^2.0.2",
-        "optionator": "^0.8.1",
-        "source-map": "~0.6.1"
+        "optionator": "^0.8.1"
       },
       "bin": {
         "escodegen": "bin/escodegen.js",
@@ -5180,7 +5180,6 @@
       "integrity": "sha512-GDhU9ntwuKyGXdZBUgTIe+vXnWj0fppUEtMDL0+idd5Sta8TGpHssn/eusA9mrPr9qNDym6SxAYZjNvCn/9RBg==",
       "dev": true,
       "dependencies": {
-        "@types/yauzl": "^2.9.1",
         "debug": "^4.1.1",
         "get-stream": "^5.1.0",
         "yauzl": "^2.10.0"
@@ -6996,7 +6995,6 @@
         "@types/node": "*",
         "anymatch": "^3.0.3",
         "fb-watchman": "^2.0.0",
-        "fsevents": "^2.1.2",
         "graceful-fs": "^4.2.4",
         "jest-regex-util": "^26.0.0",
         "jest-serializer": "^26.6.2",
@@ -15056,9 +15054,9 @@
       "dev": true
     },
     "acorn": {
-      "version": "8.0.4",
-      "resolved": "https://registry.npmjs.org/acorn/-/acorn-8.0.4.tgz",
-      "integrity": "sha512-XNP0PqF1XD19ZlLKvB7cMmnZswW4C/03pRHgirB30uSJTaS3A3V1/P4sS3HPvFmjoriPCJQs+JDSbm4bL1TxGQ=="
+      "version": "8.1.0",
+      "resolved": "https://registry.npmjs.org/acorn/-/acorn-8.1.0.tgz",
+      "integrity": "sha512-LWCF/Wn0nfHOmJ9rzQApGnxnvgfROzGilS8936rqN/lfcYkY9MYZzdMqN+2NJ4SlTc+m5HiSa+kNfDtI64dwUA=="
     },
     "acorn-globals": {
       "version": "6.0.0",
diff --git a/package.json b/package.json
index a4084d664..98a73084e 100644
--- a/package.json
+++ b/package.json
@@ -7,6 +7,7 @@
     "federalist": "npm run build-js",
     "watch-js": "webpack -w --config webpack.config.js --progress --color",
     "optimize-assets": "svgo --disable=removeViewBox -r -f assets/img",
+    "es5-safe": "find _site/assets/js/build -name '*.js' -exec cat {} \\; | acorn --ecma5 --silent",
     "viewbox": "./node_modules/.bin/svglint 'assets/img/**/*.svg'",
     "lint": "eslint spec webpack.config.js assets",
     "pretest": "if [ -z $SKIP_BUILD ]; then make build; fi",
@@ -29,6 +30,7 @@
   "keywords": [],
   "devDependencies": {
     "@axe-core/puppeteer": "^4.1.0",
+    "acorn": "^8.1.0",
     "eslint": "^7.15.0",
     "eslint-plugin-prettier": "^3.2.0",
     "get-port": "^5.1.1",