[Tests] add eslint; run more travis tests

.eslintrc

@@ -0,0 +1,17 @@
+{
+  "root": true,
+  "parserOptions": {
+    "ecmaVersion": 5,
+  },
+  "overrides": [
+    {
+      "files": "**/__tests__/**/*",
+      "parserOptions": {
+        "ecmaVersion": "2019",
+        "ecmaFeatures": {
+          "jsx": true,
+        }
+      },
+    },
+  ],
+}

.travis.yml

@@ -1,10 +1,22 @@
 language: node_js
-node_js: "node"
+os:
+ - linux
+node_js:
+  - "11"
+  - "10"
+  - "8"
+  - "6"
 cache:
   directories:
     - "node_modules"
 notifications:
   email: false
-branches:
-  only:
-  - master
+matrix:
+  fast_finish: true
+  include:
+    - node_js: "lts/*"
+      env: PRETEST=true
+script:
+  - 'if [ -n "${PRETEST-}" ]; then yarn run pretest ; fi'
+  - 'if [ -n "${TEST-}" ]; then yarn run tests-only ; fi'
+sudo: false

package.json

@@ -29,7 +29,10 @@
     "react-is": "^16.8.1"
   },
   "scripts": {
-    "test": "jest",
+    "pretest": "npm run lint",
+    "lint": "eslint .",
+    "test": "npm run tests-only",
+    "tests-only": "jest",
     "umd": "NODE_ENV=development browserify index.js -t loose-envify --standalone PropTypes -o prop-types.js",
     "umd-min": "NODE_ENV=production browserify index.js -t loose-envify -t uglifyify --standalone PropTypes  -p bundle-collapser/plugin -o | uglifyjs --compress unused,dead_code -o prop-types.min.js",
     "build": "yarn umd && yarn umd-min",
@@ -40,6 +43,7 @@
     "babel-preset-react": "^6.24.1",
     "browserify": "^14.3.0",
     "bundle-collapser": "^1.2.1",
+    "eslint": "^5.13.0",
     "jest": "^19.0.2",
     "loose-envify": "^1.4.0",
     "react": "^15.5.1",