---
title: "rerender simple expression in memo"
description: "When an expression is simple (few logical or arithmetical operators) and has a primitive result type (boolean, number, string), do not wrap it in `useMemo`. Calling `useMemo` and comparing hook dependencies may consume more resources than the expression itself."
type: skill
canonical_url: https://claudary.paisolsolutions.com/skills/rerender-simple-expression-in-memo
source: "Claudary"
difficulty: intermediate
author: "Claude Code Knowledge Pack"
date: 2026-07-10T11:46:04.709Z
license: CC-BY-4.0
attribution: "rerender simple expression in memo — Claudary (https://claudary.paisolsolutions.com/skills/rerender-simple-expression-in-memo)"
---

# rerender simple expression in memo
When an expression is simple (few logical or arithmetical operators) and has a primitive result type (boolean, number, string), do not wrap it in `useMemo`. Calling `useMemo` and comparing hook dependencies may consume more resources than the expression itself.

## Overview

---
title: Do not wrap a simple expression with a primitive result type in useMemo
impact: LOW-MEDIUM
impactDescription: wasted computation on every render
tags: rerender, useMemo, optimization
---

## Do not wrap a simple expression with a primitive result type in useMemo

When an expression is simple (few logical or arithmetical operators) and has a primitive result type (boolean, number, string), do not wrap it in `useMemo`.
Calling `useMemo` and comparing hook dependencies may consume more resources than the expression itself.

**Incorrect:**

```tsx
function Header({ user, notifications }: Props) {
  const isLoading = useMemo(() => {
    return user.isLoading || notifications.isLoading
  }, [user.isLoading, notifications.isLoading])

  if (isLoading) return <Skeleton />
  // return some markup
}
```

**Correct:**

```tsx
function Header({ user, notifications }: Props) {
  const isLoading = user.isLoading || notifications.isLoading

  if (isLoading) return <Skeleton />
  // return some markup
}
```

---

Source: [Claudary](https://claudary.paisolsolutions.com/skills/rerender-simple-expression-in-memo) · https://claudary.paisolsolutions.com