add basic linter setup

.eslintrc.json

@@ -0,0 +1,28 @@
+{
+    "env": {
+        "commonjs": true,
+        "es6": true,
+        "node": true
+    },
+    "extends": "eslint:recommended",
+    "globals": {
+        "Atomics": "readonly",
+        "SharedArrayBuffer": "readonly"
+    },
+    "ignorePatterns": ["node_modules", "test", "*example.js"],
+    "parserOptions": {
+        "ecmaVersion": 2018
+    },
+    "rules": {
+        "no-irregular-whitespace": "off",
+        "no-mixed-spaces-and-tabs": "off",
+        "no-unused-vars": [
+            "error",
+            {
+                "vars": "all",
+                "args": "none",
+                "ignoreRestSiblings": false
+            }
+        ]
+    }
+}

.travis.yml

@@ -5,7 +5,7 @@ node_js:
   - 'lts/*'
   - '10'
 cache: npm
-script: npm test
+script: npm run lint && npm test
 jobs:
   include:
     - name: e2e-test

package.json

@@ -57,6 +57,7 @@
 	},
 	"devDependencies": {
 		"db-stations": "^3.0.0",
+		"eslint": "^6.8.0",
 		"is-coordinates": "^2.0.2",
 		"is-roughly-equal": "^0.1.0",
 		"tap-spec": "^5.0.0",
@@ -67,6 +68,7 @@
 	},
 	"scripts": {
 		"e2e-test": "env NODE_ENV=dev node test/e2e/index.js | tap-spec",
+		"lint": "eslint .",
 		"test": "env NODE_ENV=dev node test/index.js | tap-spec",
 		"prepublishOnly": "npm test && npm run e2e-test"
 	}