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fetch-data

Fetching data

Last reviewed May 28, 2026 Content v20260528
Track mode
client_vue
Means
In-browser Vue TS
Reading
~1 min
Level
intermediate

This lesson

This lesson teaches Fetching data: the concepts, APIs, and habits you need before advancing in Vue.

Data fetching patterns appear in every dashboard; loading and error states are not optional polish.

You will apply Fetching data in contexts like: Dashboards and detail views fed by REST APIs with loading and error UI.

Write TypeScript, click Run—Vue 3 loads from CDN with the template compiler, mountApp shows UI in #app, and printOutput feeds the terminal.

When you can explain the previous lesson's ideas without copying starter code.

Data fetching in Vue usually runs inside onMounted, a watcher, or a composable. In this playground we simulate an API with setTimeout so you learn the state machine without CORS or flaky networks.

Typical flow

  1. Set loading to true when a request starts
  2. Store results in a ref when data arrives
  3. Capture failures in an error ref or show fallback UI
  4. Ignore stale responses if the user changes filters before the prior fetch finishes

Production note

Real apps use fetch, axios, or libraries like TanStack Query / Pinia actions. The loading → data → error pattern is the same whether data comes from REST, GraphQL, or server components in a meta-framework.

Self-check

  1. Why fetch in onMounted instead of top-level setup body?
  2. What happens if you forget to clear loading on error?

Pitfall: Fetching in bare setup without lifecycle can run twice in SSR—use onMounted in client-only playgrounds and apps.

Interview prep

Where should fetch run in Composition API?

Typically onMounted or a composable invoked from setup—set loading/error refs and guard against stale responses on unmount.

Interview tip Lesson completion confidence

Can you explain this lesson in 30 seconds without reading notes?

Not saved yet.

Playground

Runs in your browser in a sandboxed frame. Backend runners appear when this track’s profile allows them.

Check yourself

Multiple choice — immediate feedback.

Discussion

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Starter discussion topics

  • Loading state shape?
  • Mock API ok?

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