# vue/no-arrow-functions-in-watch
disallow using arrow functions to define watcher
- ⚙️ This rule is included in all of
"plugin:vue/vue3-essential","plugin:vue/essential","plugin:vue/vue3-strongly-recommended","plugin:vue/strongly-recommended","plugin:vue/vue3-recommended"and"plugin:vue/recommended".
# 📖 Rule Details
This rules disallows using arrow functions to defined watcher.The reason is arrow functions bind the parent context, so this will not be the Vue instance as you expect.(see here for more details (opens new window))
<script>
export default {
watch: {
/* ✓ GOOD */
a: function (val, oldVal) {
console.log('new: %s, old: %s', val, oldVal)
},
b: 'someMethod',
c: {
handler: function (val, oldVal) { /* ... */ },
deep: true
},
d: {
handler: 'someMethod',
immediate: true
},
e: [
'handle1',
function handle2 (val, oldVal) { /* ... */ },
{
handler: function handle3 (val, oldVal) { /* ... */ },
/* ... */
}
],
'e.f': function (val, oldVal) { /* ... */ },
/* ✗ BAD */
foo: (val, oldVal) => {
console.log('new: %s, old: %s', val, oldVal)
}
}
}
</script>
# 🔧 Options
Nothing.
# 🚀 Version
This rule was introduced in eslint-plugin-vue v7.0.0