Loading State

Loading State Overview

At its core, loading state is about doing one thing well in Redux. Once you understand the pattern, you can apply it consistently across projects and teams.

Good loading state pays off across the whole project: fewer surprises, easier collaboration, and smoother onboarding. The snippet below is a solid starting point.

import { createAsyncThunk, createSlice } from '@reduxjs/toolkit';

export const fetchUser = createAsyncThunk('user/fetch', async (id) => {
  const res = await fetch(`/api/users/${id}`);
  return res.json();
});

const userSlice = createSlice({
  name: 'user',
  initialState: { data: null, status: 'idle' },
  reducers: {},
  extraReducers: (builder) => {
    builder
      .addCase(fetchUser.pending, (s) => { s.status = 'loading'; })
      .addCase(fetchUser.fulfilled, (s, a) => { s.status = 'idle'; s.data = a.payload; });
  },
});

createAsyncThunk handles async flows and dispatches pending/fulfilled/rejected actions automatically.

Loading State Example

const slice = createSlice({ name, initialState, reducers });
const store = configureStore({ reducer: { key: slice.reducer } });
// dispatch(slice.actions.something())

• Start from a minimal Loading State example and grow it only as needed.
• Keep things explicit so Loading State behaves the same for everyone on the team.
• Name things clearly so teammates understand your Loading State at a glance.
• Verify Loading State works as expected before relying on it in important work.

Redux Cheatsheet

Quick Redux Toolkit reference related to loading state.

How Loading State Works in Redux

Loading State follows Redux's predictable data flow: components dispatch actions, reducers compute the next state from the previous state and the action, and subscribed components re-render.

createAsyncThunk handles async flows and dispatches pending/fulfilled/rejected actions automatically.

• State lives in a single, read-only store.
• Actions are the only way to describe a change.
• Reducers are pure functions that return the next state.
• Redux Toolkit removes most boilerplate with slices and thunks.

Practical Guidance for Loading State

In modern apps, loading state should use Redux Toolkit rather than hand-written Redux. Keep state minimal, colocate logic in slices, and use RTK Query for server data.

Common Mistakes

• Copying loading state commands or snippets without understanding what each part does.
• Skipping edge cases and error handling when using loading state.
• Not verifying the result of loading state before moving on.
• Over-complicating loading state before you actually need the extra flexibility.

Key Takeaways

• Loading State is a core part of working effectively with Redux.
• Start small and keep loading state focused on a single goal.
• Apply consistent patterns so loading state scales across your project.
• Practise and document loading state to keep your workflow maintainable.