React · Theory

What is useState?

Theory

64/94

What is useState?

In one line: useState is how a function component remembers a value between renders. Without it, every render would reset let n = 0. With it, n survives and the UI can change.

It is a hook — a function whose name starts with use. React only lets you call hooks in components (or other hooks). That is why the question is worded ‘what is the useState in React’ — they want hook + memory + re-render, not a blog slogan.

What is useState? — on screen — Hello Asha. useState holds name inside the function component.

Diagram

useState(false)
      │ click
      ▼
  setLiked(true)
      │
      ▼
   Like → Liked

Exam tip

Memory between renders + setter.

Example

// What is useState
import { useState } from "react";

export default function NameBox() {
  const [name, setName] = useState("Asha");
  return <p>Hello {name}</p>;
}

What is useState? — on screen: Hello Asha. useState holds name inside the function component.

Short notes

DefRemembers a value across renders.
RuleHook, top-level, function components.
TrapTreating it like a normal let.

React · Theory

What is useState?

← All stacks

Theory

64/94

What is useState?

In one line: useState is how a function component remembers a value between renders. Without it, every render would reset let n = 0. With it, n survives and the UI can change.

What is useState? — on screen — Hello Asha. useState holds name inside the function component.

Diagram

useState(false)
      │ click
      ▼
  setLiked(true)
      │
      ▼
   Like → Liked

Exam tip

Memory between renders + setter.

Example

// What is useState
import { useState } from "react";

export default function NameBox() {
  const [name, setName] = useState("Asha");
  return <p>Hello {name}</p>;
}

What is useState? — on screen: Hello Asha. useState holds name inside the function component.

Short notes

DefRemembers a value across renders.
RuleHook, top-level, function components.
TrapTreating it like a normal let.

What is useState?

Example

Short notes

Questions

What is useState?

Example

Short notes

Questions