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How Tech Works/APIs: How Apps Talk/1/4What is an API?
Essential to know
- •API stands for Application Programming Interface — a way for software to communicate
- •APIs define what operations are available and what data format to use
- •Web APIs use HTTP to communicate over the Internet
You use APIs every day. When you check the weather, pay online, or log in with Google — APIs make those connections happen. Think of a waiter at a restaurant: you tell the waiter what you want, and the kitchen handles the rest.
fetch("https://api.weather.com/forecast")
.then(res => res.json())
.then(data => {
console.log(data.temp) // 18°C
})AI Tutor
Has full context of this lesson
Can you give me a real example of an API call?
When you open a weather app, it calls GET /api/weather?city=Paris
The server responds with { "temp": 18 } — your app never touches the database directly.
How Tech Works/APIs: How Apps Talk/1/4What is an API?
Essential to know
- •API stands for Application Programming Interface — a way for software to communicate
- •APIs define what operations are available and what data format to use
- •Web APIs use HTTP to communicate over the Internet
You use APIs every day. When you check the weather, pay online, or log in with Google — APIs make those connections happen. Think of a waiter at a restaurant: you tell the waiter what you want, and the kitchen handles the rest.
fetch("https://api.weather.com/forecast")
.then(res => res.json())
.then(data => {
console.log(data.temp) // 18°C
})AI Tutor
Has full context of this lesson
Can you give me a real example of an API call?
When you open a weather app, it calls GET /api/weather?city=Paris
The server responds with { "temp": 18 } — your app never touches the database directly.
24 courses across 8 prebuilt learning paths
How it works
Q4 / 4
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How Tech Works6 modules
APIs4 modules
Deploy & Ship3 modulesRead lessons, see examples
24 courses (React, Git, Python...) with short lessons, commented code, and real-world examples.
Why does this API use POST instead of GET?
POST sends data to the server. GET only retrieves it. Here, the form submits user input.
Ask the AI tutor
Something unclear? Ask your question. The tutor explains using the context of your lesson.
Question
What happens when an API returns a 404?
Test what you learned
After each lesson, the AI asks you a question about what you just read. You answer, it corrects.
A chatbot in each lesson that knows what you're reading.
You're mid-lesson, something isn't clear — you type your question. The AI tutor has the context of the lesson and explains with your level in mind. No need to Google or switch tabs.
- You ask "why useEffect here?" — it explains with the lesson context
- It gives the reasoning, not just a code snippet
- It knows what you've already covered in the course
AI Tutor
Has full context of this lesson
Why does this use fetch() instead of a regular form to call the API?
A <form> triggers a full page reload — the browser navigates away and re-renders everything.
fetch() sends the request in the background. You update just the part that changed — no reload.
Think of a form like mailing a letter. fetch() is like a text — instant reply, no page change.
After each lesson, verify that you understood.
You click "Check me", the AI generates a question based on what you just read. You answer in your own words, and it tells you if you got it right — with an explanation if you missed something.
- The question is generated from the lesson you just read
- You answer in plain text — no multiple choice tricks
- You get instant feedback with what you missed
React/Hooks/Exercise 2/3Question
What bug is in this useEffect? What happens if the user types fast?
useEffect(() => {
fetch(`/api/search?q=${query}`)
.then(r => r.json())
.then(data => setResults(data))
}, [query])What happens when query changes faster than the network responds?
Your answer
Race condition — multiple fetches fire and older results can overwrite newer ones.
Correct!
Race condition identified. Fix: use AbortController in the cleanup.
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2 coursesReact FundamentalsM 3/5Hooks/useEffect in depth
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