Context vs stores decision in Svelte - Visual Side-by-Side Comparison

Concept Flow - Context vs stores decision

Start

↓

Need to share data?

Yes↓

Is data local to component tree?

No→Use store

Yes↓

Use context API

↓

Components access data

↓

Update data triggers UI refresh

↓

End

Decide if data is shared locally in a component tree (use context) or globally across app (use store). Components then access and update data accordingly.

Execution Sample

Svelte

import { writable } from 'svelte/store';
import { setContext, getContext } from 'svelte';

// Store example
const count = writable(0);

// Context example
setContext('key', count);

Shows creating a store and setting it in context for child components to access.

Execution Table

Step	Action	Data Location	Method Used	Result
1	Decide to share data	Local tree	Use context API	setContext called with key and data
2	Child component accesses data	Local tree	getContext with key	Receives data from context
3	Update data in context	Local tree	Update store inside context	UI updates in components using context
4	Decide to share data	Global app	Use store directly	Store created with writable()
5	Any component subscribes	Global app	Subscribe to store	Receives current data and updates
6	Update store value	Global app	Call store.set()	All subscribers update UI
7	End	-	-	Data sharing and updates complete

💡 Data sharing method chosen based on scope: context for local tree, store for global app

Variable Tracker

Variable	Start	After Step 1	After Step 3	After Step 4	After Step 6	Final
count	undefined	writable(0) in context	updated value (e.g., 1)	writable(0) global store	updated value (e.g., 2)	final updated value

Key Moments - 3 Insights

Why use context instead of a store for local data?

Context shares data only within a specific component subtree, avoiding global subscriptions. See execution_table step 1 and 2 where context is set and accessed locally.

Can stores be used inside context?

Yes, stores can be passed via context to share reactive data locally. Execution_table step 3 shows updating a store inside context triggers UI updates.

When should I choose a store over context?

Use stores when data must be shared globally across many unrelated components. Execution_table steps 4-6 show global store creation and updates.

Visual Quiz - 3 Questions

Look at the execution_table, at which step is context data accessed by a child component?

A Step 4

B Step 2

C Step 5

D Step 6

💡 Hint

Check the 'Method Used' column for 'getContext' usage in execution_table step 2

According to variable_tracker, what is the value of 'count' after step 3?

A updated value (e.g., 1)

B writable(0)

C undefined

D final updated value

💡 Hint

Look at the 'After Step 3' column for 'count' in variable_tracker

If data is shared globally, which method is used according to execution_table?

A setContext

B getContext

C writable store

D local variable

💡 Hint

See execution_table steps 4-6 describing global data sharing

Concept Snapshot

Context vs Stores Decision in Svelte:
- Use context API to share data locally within a component tree.
- Use writable stores to share data globally across the app.
- Context passes data down without global subscriptions.
- Stores provide reactive global state accessible anywhere.
- Choose based on data scope and update needs.

Full Transcript

This visual execution shows how to decide between using context or stores in Svelte for sharing data. First, if data is only needed within a component subtree, use the context API by setting data with setContext and accessing it with getContext. This keeps data local and avoids global subscriptions. If data must be shared globally across many components, create a writable store and subscribe to it wherever needed. Updates to the store automatically refresh all subscribers. The execution table traces steps for both approaches, showing when context is set and accessed, and when stores are created and updated. The variable tracker follows the store variable 'count' as it changes. Key moments clarify why and when to use each method. The quiz tests understanding of these steps. This helps beginners visually grasp the decision and flow of data sharing in Svelte.