# JavaScript URL Filename and Extension Extractor

> Extracts the file name and extension from a URL string in JavaScript, applying specific formatting rules including URL decoding, uppercase extension without a dot, and a default fallback extension.

- Skill: `ecnu-icalk/javascript-url-filename-and-extension-extractor` (Agent Skill)
- Install (CLI): `npx skillmds@latest add ecnu-icalk/javascript-url-filename-and-extension-extractor`
- Raw SKILL.md: https://api.skillmd.com/api/skills/ecnu-icalk/javascript-url-filename-and-extension-extractor/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: ECNU-ICALK (https://skillmd.com/u/ecnu-icalk)
- Updated: 2026-09-08
- Page: https://skillmd.com/skills/ecnu-icalk/javascript-url-filename-and-extension-extractor

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# JavaScript URL Filename and Extension Extractor

Extracts the file name and extension from a URL string in JavaScript, applying specific formatting rules including URL decoding, uppercase extension without a dot, and a default fallback extension.

## Prompt

# Role & Objective
Act as a JavaScript developer. Create a function to extract the file name and extension from a given URL string based on specific formatting and logic requirements.

# Operational Rules & Constraints
1. **Filename Format**: The returned filename must include the file extension (e.g., `document.pdf`).
2. **URL Decoding**: The filename must be URL-decoded (e.g., convert `%20` to spaces) using `decodeURIComponent`.
3. **Extension Format**: The returned extension must be in uppercase.
4. **Extension Punctuation**: The returned extension must NOT include the leading dot (`.`).
5. **Default Fallback**: If the URL does not contain a detectable extension, the extension must default to `HTM`.
6. **Robustness**: The function should handle standard URLs and URLs with query parameters or complex paths.

# Output Contract
Provide a JavaScript code snippet containing the function and usage examples demonstrating the rules above.

## Triggers

- extract filename and extension from url in javascript
- javascript get file extension from link
- parse url filename and extension
- url decode filename javascript