Widely availableUseful for script files that may run directly in shell environments. It has little impact on typical browser app code.
Language core Widely available

Hashbang comments

Hashbang comments allow JavaScript files to begin with a Unix-style #! line. This helps the same file work both as a command-line script and as JavaScript source.

SyntaxScriptsCompatibility

Overview

Hashbang comments allow JavaScript files to begin with a Unix-style #! line. This helps the same file work both as a command-line script and as JavaScript source.

Browser support

Feature Desktop Mobile
Chrome
Edge
Firefox
Safari
Chrome Android
Safari iOS
hashbang_comments
74
79
67
13.1
74
13.4
1+Supported (version) Not supported ※Has note Sub-feature descriptions sourced from MDN Web Docs (CC BY-SA 2.5)

Syntax

JAVASCRIPT 
#!/usr/bin/env node

console.log('Hello from CLI!');

Use cases

  • CLI entry files

    Keep a script executable from the command line while still parsing as standard JavaScript.

  • Cross-environment tooling

    Use one entry file for local tooling where both shell execution and JavaScript parsing matter.

Cautions

  • Hashbang comments are mainly about interoperability; they do not add runtime capability in the browser.
  • Only the very first line is treated specially, so placement matters.

Accessibility

  • This feature does not affect UI accessibility directly, but consistent tooling can improve developer workflows.
  • Document command-line usage clearly so scripts remain understandable to contributors.

Related links

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