ESLint

Error level

• 0 - turn the rule off
• 1 - turn the rule on as a warning (doesn't affect exit code)
• 2 - turn the rule on as an error (exit code will be 1)

extends

あらかじめ定義したのをextendsして使う

// https://github.com/vuejs/eslint-config-vue
  extends: 'vue',