Mouse Events

Q: What is the difference between onMouseEnter/onMouseLeave and onMouseOver/onMouseOut?

onMouseEnter / onMouseLeave do NOT bubble and fire only for the exact element, not its children onMouseOver / onMouseOut DO bubble, so they fire when entering/leaving child elements too Use Enter/Leave for hover state on a single element; use Over/Out when you need bubbling

Q: What is the difference between e.target and e.currentTarget?

e.target is the element that was actually clicked (could be a nested child) e.currentTarget is the element the handler is attached to If you click a inside a , e.target is the span, e.currentTarget is the button

Q: How do you detect which mouse button was pressed?

Use e.button in onMouseDown or onMouseUp: 0 = left button 1 = middle button 2 = right button Do not rely on onClick for button detection -- it is primarily for left-clicks.

Q: Gotcha: Why does onDoubleClick also fire onClick twice?

A double-click triggers: onClick -> onClick -> onDoubleClick. If your onClick performs an action, it runs twice before the double-click fires. Use a debounce timer to distinguish single from double clicks, or avoid combining both handlers on the same element.

Q: Gotcha: Why does onMouseMove cause performance issues?

onMouseMove fires very frequently (hundreds of times per second). Attaching state updates to it causes excessive re-renders. Throttle with requestAnimationFrame, use a throttle utility, or store position in a ref and only re-render when needed.

Q: What coordinate properties are available on mouse events, and how do they differ?

clientX / clientY -- relative to the viewport pageX / pageY -- relative to the document (includes scroll offset) screenX / screenY -- relative to the monitor nativeEvent.offsetX / offsetY -- relative to the target element

Handle clicks, double-clicks, hovers, and mouse movement in React components.

Mouse Event Reference

React Prop	TypeScript Type	Fires When
`onClick`	`React.MouseEvent<T>`	Element is clicked (mousedown + mouseup on same target)
`onDoubleClick`	`React.MouseEvent<T>`	Element is double-clicked
`onMouseDown`	`React.MouseEvent<T>`	Mouse button is pressed down on element
`onMouseUp`	`React.MouseEvent<T>`	Mouse button is released on element
`onMouseEnter`	`React.MouseEvent<T>`	Pointer enters the element (does NOT bubble)
`onMouseLeave`	`React.MouseEvent<T>`	Pointer leaves the element (does NOT bubble)
`onMouseOver`	`React.MouseEvent<T>`	Pointer enters the element or a child (bubbles)
`onMouseOut`	`React.MouseEvent<T>`	Pointer leaves the element or enters a child (bubbles)
`onMouseMove`	`React.MouseEvent<T>`	Pointer moves while over the element
`onContextMenu`	`React.MouseEvent<T>`	Right-click or context menu key is pressed

Recipe

Quick-reference recipe card -- copy-paste ready.

// Click handler with typed event
function ClickExample() {
  const handleClick = (e: React.MouseEvent<HTMLButtonElement>) => {
    console.log("Clicked at", e.clientX, e.clientY);
  };
 
  return <button onClick={handleClick}>Click me</button>;
}
 
// Hover with onMouseEnter / onMouseLeave
function HoverExample() {
  const [hovered, setHovered] = React.useState(false);
 
  return (
    <div
      onMouseEnter={() => setHovered(true)}
      onMouseLeave={() => setHovered(false)}
      style={{ background: hovered ? "#e0e7ff" : "#fff" }}
    >
      Hover me
    </div>
  );
}
 
// Right-click context menu
function ContextMenuExample() {
  const handleContextMenu = (e: React.MouseEvent<HTMLDivElement>) => {
    e.preventDefault();
    console.log("Custom menu at", e.clientX, e.clientY);
  };
 
  return <div onContextMenu={handleContextMenu}>Right-click me</div>;
}
 
// Double-click
function DoubleClickExample() {
  const handleDoubleClick = (e: React.MouseEvent<HTMLSpanElement>) => {
    console.log("Double-clicked");
  };
 
  return <span onDoubleClick={handleDoubleClick}>Double-click to edit</span>;
}

When to reach for this: You need to respond to mouse interactions -- clicks, hovers, right-clicks, or position tracking -- in a client component.

Working Example

"use client";
 
import { useState, useRef, useCallback } from "react";
 
type ContextMenuState = {
  visible: boolean;
  x: number;
  y: number;
};
 
export default function InteractiveCard() {
  const [hovered, setHovered] = useState(false);
  const [clickCount, setClickCount] = useState(0);
  const [contextMenu, setContextMenu] = useState<ContextMenuState>({
    visible: false,
    x: 0,
    y: 0,
  });
  const cardRef = useRef<HTMLDivElement>(null);
 
  const handleClick = useCallback(
    (e: React.MouseEvent<HTMLDivElement>) => {
      // Close context menu on regular click
      if (contextMenu.visible) {
        setContextMenu((prev) => ({ ...prev, visible: false }));
        return;
      }
      setClickCount((c) => c + 1);
    },
    [contextMenu.visible]
  );
 
  const handleContextMenu = useCallback(
    (e: React.MouseEvent<HTMLDivElement>) => {
      e.preventDefault();
      const rect = cardRef.current?.getBoundingClientRect();
      if (!rect) return;
 
      setContextMenu({
        visible: true,
        x: e.clientX - rect.left,
        y: e.clientY - rect.top,
      });
    },
    []
  );
 
  const handleMenuAction = useCallback((action: string) => {
    console.log("Menu action:", action);
    setContextMenu((prev) => ({ ...prev, visible: false }));
  }, []);
 
  return (
    <div
      ref={cardRef}
      onClick={handleClick}
      onMouseEnter={() => setHovered(true)}
      onMouseLeave={() => {
        setHovered(false);
        setContextMenu((prev) => ({ ...prev, visible: false }));
      }}
      onContextMenu={handleContextMenu}
      style={{
        position: "relative",
        padding: "24px",
        border: `2px solid ${hovered ? "#6366f1" : "#e5e7eb"}`,
        borderRadius: "12px",
        background: hovered ? "#f5f3ff" : "#fff",
        transition: "all 150ms ease",
        cursor: "pointer",
        userSelect: "none",
      }}
    >
      <h3>Interactive Card</h3>
      <p>Clicked {clickCount} times. Right-click for context menu.</p>
 
      {contextMenu.visible && (
        <ul
          style={{
            position: "absolute",
            top: contextMenu.y,
            left: contextMenu.x,
            background: "#fff",
            border: "1px solid #e5e7eb",
            borderRadius: "8px",
            boxShadow: "0 4px 12px rgba(0,0,0,0.1)",
            listStyle: "none",
            padding: "4px 0",
            margin: 0,
            zIndex: 10,
          }}
        >
          {["Edit", "Duplicate", "Delete"].map((action) => (
            <li
              key={action}
              onClick={(e) => {
                e.stopPropagation();
                handleMenuAction(action);
              }}
              onMouseEnter={(e) =>
                (e.currentTarget.style.background = "#f3f4f6")
              }
              onMouseLeave={(e) =>
                (e.currentTarget.style.background = "transparent")
              }
              style={{ padding: "8px 16px", cursor: "pointer" }}
            >
              {action}
            </li>
          ))}
        </ul>
      )}
    </div>
  );
}

What this demonstrates:

Combining onClick, onMouseEnter, onMouseLeave, and onContextMenu on a single element
Positioning a custom context menu relative to the card using getBoundingClientRect
Using e.stopPropagation() to prevent menu item clicks from triggering the card click handler
Using e.preventDefault() on onContextMenu to suppress the browser default menu
TypeScript typing for state, refs, and event handlers

Deep Dive

How It Works

React normalizes mouse events through its Synthetic Event system. Every mouse event handler receives a React.MouseEvent<T> that wraps the native MouseEvent with a consistent cross-browser interface.
React uses event delegation -- a single listener is attached at the root, not on each element. Your handler is invoked during the bubble phase by default.
onMouseEnter and onMouseLeave do NOT bubble. They fire only for the exact element, not its children. Use onMouseOver and onMouseOut if you need bubbling behavior.
The Synthetic Event is pooled and reused. If you need to access the event asynchronously (e.g., in a setTimeout), read the values you need into local variables first.

Variations

Click with data passing:

type Item = { id: string; name: string };
 
function ItemList({ items }: { items: Item[] }) {
  const handleClick = (item: Item) => (e: React.MouseEvent<HTMLLIElement>) => {
    console.log("Selected:", item.id, "at", e.clientX);
  };
 
  return (
    <ul>
      {items.map((item) => (
        <li key={item.id} onClick={handleClick(item)}>
          {item.name}
        </li>
      ))}
    </ul>
  );
}

Hover tracking with coordinates:

function HoverTracker() {
  const [position, setPosition] = useState({ x: 0, y: 0 });
 
  const handleMouseMove = useCallback(
    (e: React.MouseEvent<HTMLDivElement>) => {
      const rect = e.currentTarget.getBoundingClientRect();
      setPosition({
        x: e.clientX - rect.left,
        y: e.clientY - rect.top,
      });
    },
    []
  );
 
  return (
    <div onMouseMove={handleMouseMove} style={{ width: 300, height: 300 }}>
      Cursor at ({position.x}, {position.y})
    </div>
  );
}

Drag-start detection (mousedown + mousemove threshold):

function DragDetector() {
  const startPos = useRef<{ x: number; y: number } | null>(null);
  const [dragging, setDragging] = useState(false);
 
  const handleMouseDown = (e: React.MouseEvent<HTMLDivElement>) => {
    startPos.current = { x: e.clientX, y: e.clientY };
  };
 
  const handleMouseMove = (e: React.MouseEvent<HTMLDivElement>) => {
    if (!startPos.current) return;
    const dx = e.clientX - startPos.current.x;
    const dy = e.clientY - startPos.current.y;
    if (Math.sqrt(dx * dx + dy * dy) > 5) {
      setDragging(true);
    }
  };
 
  const handleMouseUp = () => {
    startPos.current = null;
    setDragging(false);
  };
 
  return (
    <div
      onMouseDown={handleMouseDown}
      onMouseMove={handleMouseMove}
      onMouseUp={handleMouseUp}
    >
      {dragging ? "Dragging..." : "Click and drag"}
    </div>
  );
}

Long press detection:

function LongPressButton({ onLongPress }: { onLongPress: () => void }) {
  const timerRef = useRef<ReturnType<typeof setTimeout> | null>(null);
 
  const handleMouseDown = () => {
    timerRef.current = setTimeout(onLongPress, 600);
  };
 
  const handleMouseUp = () => {
    if (timerRef.current) clearTimeout(timerRef.current);
  };
 
  return (
    <button onMouseDown={handleMouseDown} onMouseUp={handleMouseUp}>
      Long press me
    </button>
  );
}

Right-click context menu with portal:

import { createPortal } from "react-dom";
 
function ContextMenuPortal({
  x,
  y,
  onClose,
}: {
  x: number;
  y: number;
  onClose: () => void;
}) {
  return createPortal(
    <div
      style={{ position: "fixed", top: y, left: x, zIndex: 9999 }}
      onClick={onClose}
    >
      <ul style={{ background: "#fff", border: "1px solid #ddd", padding: 8 }}>
        <li>Copy</li>
        <li>Paste</li>
      </ul>
    </div>,
    document.body
  );
}

TypeScript Notes

// The generic T specifies the element type for e.currentTarget
const handleClick = (e: React.MouseEvent<HTMLButtonElement>) => {
  e.currentTarget; // HTMLButtonElement -- the element the handler is attached to
  e.target;        // EventTarget -- the actual element clicked (could be a child)
};
 
// Use HTMLElement as a generic fallback when the exact element varies
const handleAny = (e: React.MouseEvent<HTMLElement>) => {
  e.currentTarget.dataset.id; // works for any HTML element
};
 
// Narrowing e.target (it is typed as EventTarget, not Element)
const handleDelegated = (e: React.MouseEvent<HTMLUListElement>) => {
  const target = e.target as HTMLElement;
  if (target.tagName === "LI") {
    console.log(target.textContent);
  }
};
 
// Mouse button detection
const handleMouseDown = (e: React.MouseEvent<HTMLDivElement>) => {
  // e.button: 0 = left, 1 = middle, 2 = right
  if (e.button === 2) console.log("Right click");
};
 
// Coordinates available on every mouse event
// e.clientX / e.clientY -- relative to viewport
// e.pageX / e.pageY -- relative to document
// e.screenX / e.screenY -- relative to monitor
// e.nativeEvent.offsetX / offsetY -- relative to target element

Gotchas

onMouseEnter/onMouseLeave vs onMouseOver/onMouseOut -- onMouseEnter and onMouseLeave do NOT bubble and do NOT fire when moving between child elements. onMouseOver and onMouseOut DO bubble, so they fire when entering/leaving children too. Use the wrong pair and hover states will flicker on nested elements.
Creating new arrow functions in JSX on every render -- Writing onClick={() => handleClick(id)} creates a new function reference each render, which can cause unnecessary re-renders in child components that rely on referential equality. Fix: Use useCallback or extract the handler to a stable reference. For lists, consider a child component that receives the item and attaches its own handler.
onClick fires on ANY mouse button by default -- React's onClick fires for left-clicks only in most browsers, but this is not guaranteed for all elements and browsers. If you need to distinguish buttons, check e.button in onMouseDown or onMouseUp.
e.target vs e.currentTarget confusion -- e.target is the element that was actually clicked (could be a child). e.currentTarget is the element the handler is attached to. If you click a <span> inside a <button>, e.target is the span, e.currentTarget is the button. Accessing properties like .value or .dataset on e.target requires type narrowing.
onDoubleClick fires two onClick events first -- A double-click triggers: onClick -> onClick -> onDoubleClick. If your onClick handler performs an action, you will get that action twice before the double-click fires. Fix: Use a debounce timer to distinguish single from double clicks, or avoid combining both on the same element.
Synthetic events are nullified after the handler -- Accessing e.clientX inside a setTimeout or after an await returns null because React recycles the event object. Fix: Read values into local variables before any async operation: const x = e.clientX;.
onMouseMove fires very frequently -- Attaching state updates to onMouseMove can cause hundreds of re-renders per second. Fix: Throttle with requestAnimationFrame or a throttle utility, or use a ref to store position and only re-render when needed.

Alternatives

Alternative	Use When	Don't Use When
Pointer Events (`onPointerDown`, etc.)	You need to support touch, pen, and mouse uniformly	You only target mouse on desktop
CSS `:hover`	Hover styles only, no JS logic needed	You need to track hover state or coordinates in JS
Drag and Drop API (`onDragStart`, etc.)	You need full drag-and-drop with data transfer	You just need click-and-drag movement detection
`addEventListener` in `useEffect`	You need global listeners (e.g., document-level mouse tracking)	The event is scoped to a specific element
Third-party libraries (dnd-kit, Framer Motion)	Complex drag, gestures, or animation tied to mouse position	Simple click or hover handlers

FAQs

What is the difference between onMouseEnter/onMouseLeave and onMouseOver/onMouseOut?

onMouseEnter / onMouseLeave do NOT bubble and fire only for the exact element, not its children
onMouseOver / onMouseOut DO bubble, so they fire when entering/leaving child elements too
Use Enter/Leave for hover state on a single element; use Over/Out when you need bubbling

What is the difference between e.target and e.currentTarget?

e.target is the element that was actually clicked (could be a nested child)
e.currentTarget is the element the handler is attached to
If you click a <span> inside a <button>, e.target is the span, e.currentTarget is the button

How do you detect which mouse button was pressed?

Use e.button in onMouseDown or onMouseUp:

0 = left button
1 = middle button
2 = right button

Do not rely on onClick for button detection -- it is primarily for left-clicks.

How do you implement a custom right-click context menu?

const handleContextMenu = (e: React.MouseEvent<HTMLDivElement>) => {
  e.preventDefault(); // suppress browser default menu
  setMenu({ visible: true, x: e.clientX, y: e.clientY });
};
return <div onContextMenu={handleContextMenu}>Right-click me</div>;

Gotcha: Why does onDoubleClick also fire onClick twice?

A double-click triggers: onClick -> onClick -> onDoubleClick. If your onClick performs an action, it runs twice before the double-click fires. Use a debounce timer to distinguish single from double clicks, or avoid combining both handlers on the same element.

Why can't you access e.clientX inside a setTimeout or after an await?

React's synthetic events are nullified after the handler returns. Accessing properties later gives null. Read values into local variables before any async operation: const x = e.clientX;.

How do you pass data to a click handler in a list without creating a new function on every render?

function ItemList({ items }: { items: Item[] }) {
  const handleClick = (item: Item) =>
    (e: React.MouseEvent<HTMLLIElement>) => {
      console.log("Selected:", item.id);
    };
 
  return (
    <ul>
      {items.map((item) => (
        <li key={item.id} onClick={handleClick(item)}>{item.name}</li>
      ))}
    </ul>
  );
}

For better performance, extract each item into a child component with its own stable handler.

Gotcha: Why does onMouseMove cause performance issues?

onMouseMove fires very frequently (hundreds of times per second). Attaching state updates to it causes excessive re-renders. Throttle with requestAnimationFrame, use a throttle utility, or store position in a ref and only re-render when needed.

How do you implement long press detection with mouse events?

const timerRef = useRef<ReturnType<typeof setTimeout> | null>(null);
const handleMouseDown = () => {
  timerRef.current = setTimeout(onLongPress, 600);
};
const handleMouseUp = () => {
  if (timerRef.current) clearTimeout(timerRef.current);
};

What coordinate properties are available on mouse events, and how do they differ?

clientX / clientY -- relative to the viewport
pageX / pageY -- relative to the document (includes scroll offset)
screenX / screenY -- relative to the monitor
nativeEvent.offsetX / offsetY -- relative to the target element

What is the correct TypeScript generic type for mouse event handlers?

// Specific element type
const handleClick = (e: React.MouseEvent<HTMLButtonElement>) => {
  e.currentTarget; // HTMLButtonElement
};
 
// Generic fallback for any HTML element
const handleAny = (e: React.MouseEvent<HTMLElement>) => {
  e.currentTarget.dataset.id; // works for any element
};

How do you narrow the type of e.target when using event delegation in TypeScript?

const handleDelegated = (e: React.MouseEvent<HTMLUListElement>) => {
  // e.target is typed as EventTarget, not Element
  const target = e.target as HTMLElement;
  if (target.tagName === "LI") {
    console.log(target.textContent);
  }
};

Keyboard Events -- Responding to key presses and keyboard shortcuts
Form Events -- Handling form submissions and input changes

Mouse Event Reference

React Prop	TypeScript Type	Fires When
`onClick`	`React.MouseEvent<T>`	Element is clicked (mousedown + mouseup on same target)
`onDoubleClick`	`React.MouseEvent<T>`	Element is double-clicked
`onMouseDown`	`React.MouseEvent<T>`	Mouse button is pressed down on element
`onMouseUp`	`React.MouseEvent<T>`	Mouse button is released on element
`onMouseEnter`	`React.MouseEvent<T>`	Pointer enters the element (does NOT bubble)
`onMouseLeave`	`React.MouseEvent<T>`	Pointer leaves the element (does NOT bubble)
`onMouseOver`	`React.MouseEvent<T>`	Pointer enters the element or a child (bubbles)
`onMouseOut`	`React.MouseEvent<T>`	Pointer leaves the element or enters a child (bubbles)
`onMouseMove`	`React.MouseEvent<T>`	Pointer moves while over the element
`onContextMenu`	`React.MouseEvent<T>`	Right-click or context menu key is pressed

Recipe

Quick-reference recipe card -- copy-paste ready.

// Click handler with typed event
function ClickExample() {
  const handleClick = (e: React.MouseEvent<HTMLButtonElement>) => {
    console.log("Clicked at", e.clientX, e.clientY);
  };
 
  return <button onClick={handleClick}>Click me</button>;
}
 
// Hover with onMouseEnter / onMouseLeave
function HoverExample() {
  const [hovered, setHovered] = React.useState(false);
 
  return (
    <div
      onMouseEnter={() => setHovered(true)}
      onMouseLeave={() => setHovered(false)}
      style={{ background: hovered ? "#e0e7ff" : "#fff" }}
    >
      Hover me
    </div>
  );
}
 
// Right-click context menu
function ContextMenuExample() {
  const handleContextMenu = (e: React.MouseEvent<HTMLDivElement>) => {
    e.preventDefault();
    console.log("Custom menu at", e.clientX, e.clientY);
  };
 
  return <div onContextMenu={handleContextMenu}>Right-click me</div>;
}
 
// Double-click
function DoubleClickExample() {
  const handleDoubleClick = (e: React.MouseEvent<HTMLSpanElement>) => {
    console.log("Double-clicked");
  };
 
  return <span onDoubleClick={handleDoubleClick}>Double-click to edit</span>;
}

When to reach for this: You need to respond to mouse interactions -- clicks, hovers, right-clicks, or position tracking -- in a client component.

Working Example

"use client";
 
import { useState, useRef, useCallback } from "react";
 
type ContextMenuState = {
  visible: boolean;
  x: number;
  y: number;
};
 
export default function InteractiveCard() {
  const [hovered, setHovered] = useState(false);
  const [clickCount, setClickCount] = useState(0);
  const [contextMenu, setContextMenu] = useState<ContextMenuState>({
    visible: false,
    x: 0,
    y: 0,
  });
  const cardRef = useRef<HTMLDivElement>(null);
 
  const handleClick = useCallback(
    (e: React.MouseEvent<HTMLDivElement>) => {
      // Close context menu on regular click
      if (contextMenu.visible) {
        setContextMenu((prev) => ({ ...prev, visible: false }));
        return;
      }
      setClickCount((c) => c + 1);
    },
    [contextMenu.visible]
  );
 
  const handleContextMenu = useCallback(
    (e: React.MouseEvent<HTMLDivElement>) => {
      e.preventDefault();
      const rect = cardRef.current?.getBoundingClientRect();
      if (!rect) return;
 
      setContextMenu({
        visible: true,
        x: e.clientX - rect.left,
        y: e.clientY - rect.top,
      });
    },
    []
  );
 
  const handleMenuAction = useCallback((action: string) => {
    console.log("Menu action:", action);
    setContextMenu((prev) => ({ ...prev, visible: false }));
  }, []);
 
  return (
    <div
      ref={cardRef}
      onClick={handleClick}
      onMouseEnter={() => setHovered(true)}
      onMouseLeave={() => {
        setHovered(false);
        setContextMenu((prev) => ({ ...prev, visible: false }));
      }}
      onContextMenu={handleContextMenu}
      style={{
        position: "relative",
        padding: "24px",
        border: `2px solid ${hovered ? "#6366f1" : "#e5e7eb"}`,
        borderRadius: "12px",
        background: hovered ? "#f5f3ff" : "#fff",
        transition: "all 150ms ease",
        cursor: "pointer",
        userSelect: "none",
      }}
    >
      <h3>Interactive Card</h3>
      <p>Clicked {clickCount} times. Right-click for context menu.</p>
 
      {contextMenu.visible && (
        <ul
          style={{
            position: "absolute",
            top: contextMenu.y,
            left: contextMenu.x,
            background: "#fff",
            border: "1px solid #e5e7eb",
            borderRadius: "8px",
            boxShadow: "0 4px 12px rgba(0,0,0,0.1)",
            listStyle: "none",
            padding: "4px 0",
            margin: 0,
            zIndex: 10,
          }}
        >
          {["Edit", "Duplicate", "Delete"].map((action) => (
            <li
              key={action}
              onClick={(e) => {
                e.stopPropagation();
                handleMenuAction(action);
              }}
              onMouseEnter={(e) =>
                (e.currentTarget.style.background = "#f3f4f6")
              }
              onMouseLeave={(e) =>
                (e.currentTarget.style.background = "transparent")
              }
              style={{ padding: "8px 16px", cursor: "pointer" }}
            >
              {action}
            </li>
          ))}
        </ul>
      )}
    </div>
  );
}

What this demonstrates:

Combining onClick, onMouseEnter, onMouseLeave, and onContextMenu on a single element
Positioning a custom context menu relative to the card using getBoundingClientRect
Using e.stopPropagation() to prevent menu item clicks from triggering the card click handler
Using e.preventDefault() on onContextMenu to suppress the browser default menu
TypeScript typing for state, refs, and event handlers

Deep Dive

How It Works

React normalizes mouse events through its Synthetic Event system. Every mouse event handler receives a React.MouseEvent<T> that wraps the native MouseEvent with a consistent cross-browser interface.
React uses event delegation -- a single listener is attached at the root, not on each element. Your handler is invoked during the bubble phase by default.
onMouseEnter and onMouseLeave do NOT bubble. They fire only for the exact element, not its children. Use onMouseOver and onMouseOut if you need bubbling behavior.
The Synthetic Event is pooled and reused. If you need to access the event asynchronously (e.g., in a setTimeout), read the values you need into local variables first.

Variations

Click with data passing:

type Item = { id: string; name: string };
 
function ItemList({ items }: { items: Item[] }) {
  const handleClick = (item: Item) => (e: React.MouseEvent<HTMLLIElement>) => {
    console.log("Selected:", item.id, "at", e.clientX);
  };
 
  return (
    <ul>
      {items.map((item) => (
        <li key={item.id} onClick={handleClick(item)}>
          {item.name}
        </li>
      ))}
    </ul>
  );
}

Hover tracking with coordinates:

function HoverTracker() {
  const [position, setPosition] = useState({ x: 0, y: 0 });
 
  const handleMouseMove = useCallback(
    (e: React.MouseEvent<HTMLDivElement>) => {
      const rect = e.currentTarget.getBoundingClientRect();
      setPosition({
        x: e.clientX - rect.left,
        y: e.clientY - rect.top,
      });
    },
    []
  );
 
  return (
    <div onMouseMove={handleMouseMove} style={{ width: 300, height: 300 }}>
      Cursor at ({position.x}, {position.y})
    </div>
  );
}

Drag-start detection (mousedown + mousemove threshold):

function DragDetector() {
  const startPos = useRef<{ x: number; y: number } | null>(null);
  const [dragging, setDragging] = useState(false);
 
  const handleMouseDown = (e: React.MouseEvent<HTMLDivElement>) => {
    startPos.current = { x: e.clientX, y: e.clientY };
  };
 
  const handleMouseMove = (e: React.MouseEvent<HTMLDivElement>) => {
    if (!startPos.current) return;
    const dx = e.clientX - startPos.current.x;
    const dy = e.clientY - startPos.current.y;
    if (Math.sqrt(dx * dx + dy * dy) > 5) {
      setDragging(true);
    }
  };
 
  const handleMouseUp = () => {
    startPos.current = null;
    setDragging(false);
  };
 
  return (
    <div
      onMouseDown={handleMouseDown}
      onMouseMove={handleMouseMove}
      onMouseUp={handleMouseUp}
    >
      {dragging ? "Dragging..." : "Click and drag"}
    </div>
  );
}

Long press detection:

function LongPressButton({ onLongPress }: { onLongPress: () => void }) {
  const timerRef = useRef<ReturnType<typeof setTimeout> | null>(null);
 
  const handleMouseDown = () => {
    timerRef.current = setTimeout(onLongPress, 600);
  };
 
  const handleMouseUp = () => {
    if (timerRef.current) clearTimeout(timerRef.current);
  };
 
  return (
    <button onMouseDown={handleMouseDown} onMouseUp={handleMouseUp}>
      Long press me
    </button>
  );
}

Right-click context menu with portal:

import { createPortal } from "react-dom";
 
function ContextMenuPortal({
  x,
  y,
  onClose,
}: {
  x: number;
  y: number;
  onClose: () => void;
}) {
  return createPortal(
    <div
      style={{ position: "fixed", top: y, left: x, zIndex: 9999 }}
      onClick={onClose}
    >
      <ul style={{ background: "#fff", border: "1px solid #ddd", padding: 8 }}>
        <li>Copy</li>
        <li>Paste</li>
      </ul>
    </div>,
    document.body
  );
}

TypeScript Notes

// The generic T specifies the element type for e.currentTarget
const handleClick = (e: React.MouseEvent<HTMLButtonElement>) => {
  e.currentTarget; // HTMLButtonElement -- the element the handler is attached to
  e.target;        // EventTarget -- the actual element clicked (could be a child)
};
 
// Use HTMLElement as a generic fallback when the exact element varies
const handleAny = (e: React.MouseEvent<HTMLElement>) => {
  e.currentTarget.dataset.id; // works for any HTML element
};
 
// Narrowing e.target (it is typed as EventTarget, not Element)
const handleDelegated = (e: React.MouseEvent<HTMLUListElement>) => {
  const target = e.target as HTMLElement;
  if (target.tagName === "LI") {
    console.log(target.textContent);
  }
};
 
// Mouse button detection
const handleMouseDown = (e: React.MouseEvent<HTMLDivElement>) => {
  // e.button: 0 = left, 1 = middle, 2 = right
  if (e.button === 2) console.log("Right click");
};
 
// Coordinates available on every mouse event
// e.clientX / e.clientY -- relative to viewport
// e.pageX / e.pageY -- relative to document
// e.screenX / e.screenY -- relative to monitor
// e.nativeEvent.offsetX / offsetY -- relative to target element

Gotchas

onMouseEnter/onMouseLeave vs onMouseOver/onMouseOut -- onMouseEnter and onMouseLeave do NOT bubble and do NOT fire when moving between child elements. onMouseOver and onMouseOut DO bubble, so they fire when entering/leaving children too. Use the wrong pair and hover states will flicker on nested elements.
Creating new arrow functions in JSX on every render -- Writing onClick={() => handleClick(id)} creates a new function reference each render, which can cause unnecessary re-renders in child components that rely on referential equality. Fix: Use useCallback or extract the handler to a stable reference. For lists, consider a child component that receives the item and attaches its own handler.
onClick fires on ANY mouse button by default -- React's onClick fires for left-clicks only in most browsers, but this is not guaranteed for all elements and browsers. If you need to distinguish buttons, check e.button in onMouseDown or onMouseUp.
e.target vs e.currentTarget confusion -- e.target is the element that was actually clicked (could be a child). e.currentTarget is the element the handler is attached to. If you click a <span> inside a <button>, e.target is the span, e.currentTarget is the button. Accessing properties like .value or .dataset on e.target requires type narrowing.
onDoubleClick fires two onClick events first -- A double-click triggers: onClick -> onClick -> onDoubleClick. If your onClick handler performs an action, you will get that action twice before the double-click fires. Fix: Use a debounce timer to distinguish single from double clicks, or avoid combining both on the same element.
Synthetic events are nullified after the handler -- Accessing e.clientX inside a setTimeout or after an await returns null because React recycles the event object. Fix: Read values into local variables before any async operation: const x = e.clientX;.
onMouseMove fires very frequently -- Attaching state updates to onMouseMove can cause hundreds of re-renders per second. Fix: Throttle with requestAnimationFrame or a throttle utility, or use a ref to store position and only re-render when needed.

Alternatives

Alternative	Use When	Don't Use When
Pointer Events (`onPointerDown`, etc.)	You need to support touch, pen, and mouse uniformly	You only target mouse on desktop
CSS `:hover`	Hover styles only, no JS logic needed	You need to track hover state or coordinates in JS
Drag and Drop API (`onDragStart`, etc.)	You need full drag-and-drop with data transfer	You just need click-and-drag movement detection
`addEventListener` in `useEffect`	You need global listeners (e.g., document-level mouse tracking)	The event is scoped to a specific element
Third-party libraries (dnd-kit, Framer Motion)	Complex drag, gestures, or animation tied to mouse position	Simple click or hover handlers

FAQs

What is the difference between onMouseEnter/onMouseLeave and onMouseOver/onMouseOut?

onMouseEnter / onMouseLeave do NOT bubble and fire only for the exact element, not its children
onMouseOver / onMouseOut DO bubble, so they fire when entering/leaving child elements too
Use Enter/Leave for hover state on a single element; use Over/Out when you need bubbling

What is the difference between e.target and e.currentTarget?

e.target is the element that was actually clicked (could be a nested child)
e.currentTarget is the element the handler is attached to
If you click a <span> inside a <button>, e.target is the span, e.currentTarget is the button

How do you detect which mouse button was pressed?

Use e.button in onMouseDown or onMouseUp:

0 = left button
1 = middle button
2 = right button

Do not rely on onClick for button detection -- it is primarily for left-clicks.

How do you implement a custom right-click context menu?

const handleContextMenu = (e: React.MouseEvent<HTMLDivElement>) => {
  e.preventDefault(); // suppress browser default menu
  setMenu({ visible: true, x: e.clientX, y: e.clientY });
};
return <div onContextMenu={handleContextMenu}>Right-click me</div>;

Gotcha: Why does onDoubleClick also fire onClick twice?

Why can't you access e.clientX inside a setTimeout or after an await?

React's synthetic events are nullified after the handler returns. Accessing properties later gives null. Read values into local variables before any async operation: const x = e.clientX;.

How do you pass data to a click handler in a list without creating a new function on every render?

function ItemList({ items }: { items: Item[] }) {
  const handleClick = (item: Item) =>
    (e: React.MouseEvent<HTMLLIElement>) => {
      console.log("Selected:", item.id);
    };
 
  return (
    <ul>
      {items.map((item) => (
        <li key={item.id} onClick={handleClick(item)}>{item.name}</li>
      ))}
    </ul>
  );
}

For better performance, extract each item into a child component with its own stable handler.

Gotcha: Why does onMouseMove cause performance issues?

How do you implement long press detection with mouse events?

const timerRef = useRef<ReturnType<typeof setTimeout> | null>(null);
const handleMouseDown = () => {
  timerRef.current = setTimeout(onLongPress, 600);
};
const handleMouseUp = () => {
  if (timerRef.current) clearTimeout(timerRef.current);
};

What coordinate properties are available on mouse events, and how do they differ?

clientX / clientY -- relative to the viewport
pageX / pageY -- relative to the document (includes scroll offset)
screenX / screenY -- relative to the monitor
nativeEvent.offsetX / offsetY -- relative to the target element

What is the correct TypeScript generic type for mouse event handlers?

// Specific element type
const handleClick = (e: React.MouseEvent<HTMLButtonElement>) => {
  e.currentTarget; // HTMLButtonElement
};
 
// Generic fallback for any HTML element
const handleAny = (e: React.MouseEvent<HTMLElement>) => {
  e.currentTarget.dataset.id; // works for any element
};

How do you narrow the type of e.target when using event delegation in TypeScript?

const handleDelegated = (e: React.MouseEvent<HTMLUListElement>) => {
  // e.target is typed as EventTarget, not Element
  const target = e.target as HTMLElement;
  if (target.tagName === "LI") {
    console.log(target.textContent);
  }
};

Keyboard Events -- Responding to key presses and keyboard shortcuts
Form Events -- Handling form submissions and input changes

Mouse Events

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Mouse Events