add: 只出现一次的数字等

.eslintrc.js

@@ -0,0 +1,19 @@
+module.exports = {
+  root: true,
+  parserOptions: {
+    parser: 'babel-eslint',
+    ecmaVersion: 2017,
+    sourceType: 'module'
+  },
+  env: {
+    browser: true,
+    node: true
+  },
+  extends: ['standard', 'plugin:jest/recommended'],
+  rules: {
+    // allow async-await
+    'generator-star-spacing': 'off',
+    // allow debugger during development
+    'no-debugger': process.env.NODE_ENV === 'production' ? 'error' : 'off'
+  }
+}