diff --git a/.eslintrc b/.eslintrc
new file mode 100644
index 0000000..267d27e
--- /dev/null
+++ b/.eslintrc
@@ -0,0 +1,20 @@
+{
+    "root": true,
+
+    "extends": "@ljharb",
+
+    "rules": {
+        "array-bracket-newline": 0,
+        "array-bracket-spacing": 1,
+        "indent": [2, 4],
+    },
+
+    "overrides": [
+        {
+            "files": "example/**",
+            "rules": {
+                "no-console": 0,
+            },
+        },
+    ],
+}
diff --git a/example/map.js b/example/map.js
index 3365621..e4c538c 100644
--- a/example/map.js
+++ b/example/map.js
@@ -1,3 +1,5 @@
+'use strict';
+
 var concatMap = require('../');
 var xs = [ 1, 2, 3, 4, 5, 6 ];
 var ys = concatMap(xs, function (x) {
diff --git a/index.js b/index.js
index b29a781..3b0e9d3 100644
--- a/index.js
+++ b/index.js
@@ -1,13 +1,18 @@
+'use strict';
+
+var isArray = Array.isArray || function (xs) {
+    return Object.prototype.toString.call(xs) === '[object Array]';
+};
+
 module.exports = function (xs, fn) {
     var res = [];
     for (var i = 0; i < xs.length; i++) {
         var x = fn(xs[i], i);
-        if (isArray(x)) res.push.apply(res, x);
-        else res.push(x);
+        if (isArray(x)) {
+            res.push.apply(res, x);
+        } else {
+            res.push(x);
+        }
     }
     return res;
 };
-
-var isArray = Array.isArray || function (xs) {
-    return Object.prototype.toString.call(xs) === '[object Array]';
-};
diff --git a/package.json b/package.json
index ecc1879..befaab9 100644
--- a/package.json
+++ b/package.json
@@ -19,12 +19,16 @@
         "test": "test"
     },
     "scripts": {
+        "lint": "eslint --ext=js,mjs .",
+        "pretest": "npm run lint",
         "tests-only": "tape 'test/**/*.js'",
         "test": "npm run tests-only",
         "posttest": "aud --production"
     },
     "devDependencies": {
+        "@ljharb/eslint-config": "^21.0.0",
         "aud": "^2.0.1",
+        "eslint": "=8.8.0",
         "tape": "^5.6.1"
     },
     "license": "MIT",
diff --git a/test/map.js b/test/map.js
index fdbd702..5c877ad 100644
--- a/test/map.js
+++ b/test/map.js
@@ -1,3 +1,5 @@
+'use strict';
+
 var concatMap = require('../');
 var test = require('tape');