implements Keyword

Syntax

class Name implements InterfaceName { }

Examples

interface Printable {
  print(): void;
}

interface Serializable {
  serialize(): string;
}

class Document implements Printable, Serializable {
  constructor(private content: string) {}

  print(): void {
    console.log(this.content);
  }

  serialize(): string {
    return JSON.stringify({ content: this.content });
  }
}
// If Document were missing either method, TypeScript would flag it immediately

Best practices

• Use implements to guarantee a class provides all the members a given interface requires, catching missing implementations at compile time
• A class can implement multiple interfaces at once, comma-separated - useful for composing several small, focused contracts
• Remember implements provides no code - it is purely a type-level check; use extends when you actually want to inherit real behavior
• Combine implements with an interface exported from a shared location when multiple classes across a codebase need to honor the same contract

At a glance

Purpose

Static types for JavaScript

File extension

.ts · .tsx

Runs in

Compiled to JavaScript

Usually used with

JavaScript and its ecosystem

Specifications & further reading

• TypeScript Handbook

Related TypeScript documentation