How do you select a single element by its ID in JavaScript?

Call document.getElementById("id") (no #), which returns the matching element or null if none exists.

const element = document.getElementById("myButton");

Key characteristics:

• Returns a single element (IDs must be unique)
• Returns null if no element matches
• Fastest selection method (IDs are indexed)
• Does NOT include the # symbol (unlike CSS)

Common mistake:

// Wrong - don't use #
document.getElementById("#myButton");

// Correct
document.getElementById("myButton");