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TypeScript Academy · Lesson

Props & children; event handlers; refs

Define typed props and children; wire up event handlers safely; create and use refs to access DOM nodes.

Props & children; event handlers; refs is a free TypeScript Academy lesson on CoddyKit — lesson 1 of 3. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the TypeScript Academy learning path, one of 3 lessons in the course, and your progress syncs across the web and the CoddyKit app.

Intro

Goal: Build typed React components: define props (with children), attach event handlers with precise types, and focus an input using refs.

  • Typed props interfaces
  • Event handler types
  • Refs for DOM access

Typed props

Declare a props interface; use optional props and narrow with union literals. Keep defaults inside the component.

import React from "react"

interface BadgeProps {
  text: string
  color?: "primary" | "success" | "warning"
}

export function Badge({ text, color = "primary" }: BadgeProps) {
  const bg = color === "success" ? "#16a34a" : color === "warning" ? "#d97706" : "#2563eb"
  return <span style={{ backgroundColor: bg, color: "white", padding: 4, borderRadius: 6 }}>{text}</span>
}

export default function App() {
  return (
    <div style={{ display: "grid", gap: 8 }}>
      <Badge text="Saved" color="success" />
      <Badge text="Warn" color="warning" />
    </div>
  )
}

Children

Use PropsWithChildren<T> (or React.PropsWithChildren) to add a typed children slot to your props.

import React, { PropsWithChildren } from "react"

type CardProps = PropsWithChildren<{ title: string }>

function Card({ title, children }: CardProps) {
  return (
    <div style={{ border: "1px solid #e5e7eb", padding: 12, borderRadius: 8 }}>
      <h3 style={{ margin: 0 }}>{title}</h3>
      <div>{children}</div>
    </div>
  )
}

export default function App() {
  return (
    <Card title="Dashboard">
      <p>Children are typed automatically.</p>
    </Card>
  )
}

Event handlers

Prefer React.MouseEvent<Element> and React.ChangeEvent<HTMLInputElement>. They expose typed target/currentTarget.

import React from "react"

export default function App() {
  const handleClick = (e: React.MouseEvent<HTMLButtonElement>) => {
    console.log("clicked", e.currentTarget.name)
  }

  const handleChange = (e: React.ChangeEvent<HTMLInputElement>) => {
    console.log("value", e.target.value)
  }

  return (
    <div style={{ display: "grid", gap: 8 }}>
      <input name="n" onChange={handleChange} placeholder="Type here" />
      <button name="ok" onClick={handleClick}>Confirm</button>
    </div>
  )
}

Refs: DOM access

useRef<HTMLInputElement>(null) keeps a nullable ref; use optional chaining to access the DOM node safely.

import React, { useRef } from "react"

export default function App() {
  const inputRef = useRef<HTMLInputElement>(null)

  const focusInput = () => {
    inputRef.current?.focus()
  }

  return (
    <div style={{ display: "grid", gap: 8 }}>
      <input ref={inputRef} placeholder="Focus me" />
      <button onClick={focusInput}>Focus</button>
    </div>
  )
}

Forwarding refs

forwardRef lets parents access a child DOM node. Provide the element type for precise typing.

import React, { forwardRef } from "react"

type TextInputProps = { label: string }

const TextInput = forwardRef<HTMLInputElement, TextInputProps>(function TextInput({ label }, ref) {
  return (
    <label style={{ display: "grid", gap: 4 }}>
      <span>{label}</span>
      <input ref={ref} />
    </label>
  )
})

export default function App() {
  const setRef = (el: HTMLInputElement | null) => { if (el) el.focus() }
  return <TextInput ref={setRef} label="Auto focus" />
}

Events typing check

Quick check: What is a correct type for a button click handler?

Recap

Recap: Define props (with children), type your events precisely, and use refs (including forwardRef) to access DOM nodes safely.

Frequently asked questions

Is the “Props & children; event handlers; refs” lesson free?

Yes — the full text of “Props & children; event handlers; refs” is free to read here on the web, and the TypeScript Academy course includes 3 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the TypeScript Academy course, upgrade to CoddyKit PRO.

What will I learn in “Props & children; event handlers; refs”?

Define typed props and children; wire up event handlers safely; create and use refs to access DOM nodes. You practise TypeScript Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start TypeScript Academy?

No prior experience is required. TypeScript Academy on CoddyKit is structured for beginners through advanced learners; this is — lesson 1 of 3, so you can start here or from the beginning and move at your own pace.

How long does the “Props & children; event handlers; refs” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this TypeScript Academy lesson?

Yes. Every TypeScript Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

All lessons in this course

  1. Props & children; event handlers; refs
  2. State & reducers; Context typing
  3. Component generics — intro
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