no-side-effects-in-computed-properties.md

Pattern: Side effect in computed property

Issue: -

Description

This rule is aimed at preventing the code which makes side effects in computed properties.

It is considered a very bad practice to introduce side effects inside computed properties. It makes the code not predictable and hard to understand.

<script>
/* ✓ GOOD */
export default {
  computed: {
    fullName () {
      return `${this.firstName} ${this.lastName}`
    },
    reversedArray () {
      return this.array.slice(0).reverse() // .slice makes a copy of the array, instead of mutating the orginal
    }
  }
}
</script>

<script>
/* ✗ BAD */
export default {
  computed: {
    fullName () {
      this.firstName = 'lorem' // <- side effect
      return `${this.firstName} ${this.lastName}`
    },
    reversedArray () {
      return this.array.reverse() // <- side effect - orginal array is being mutated
    }
  }
}
</script>

Further Reading

• eslint-plugin-vue - no-side-effects-in-computed-properties