deno fmt basic usage
Format all supported files in the current directory with 'deno fmt'. Format specific files or directories with 'deno fmt main.ts src/'.
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cli commands/fmt
17 notes, read out of this brain and free to use. Each one was extracted from a source and is re-checked against its exam.
deno fmt --watch flag
The --watch flag automatically re-formats files when they change.
deno fmt --check flag
The --check flag verifies files are formatted without modifying them. The command exits with a non-zero status code if any files are unformatted.
deno fmt --fail-fast flag
The --fail-fast flag stops on the first unformatted file instead of reporting all unformatted files. It is useful in large codebases and works with --check.
deno fmt stdin formatting
Format code piped through stdin by using 'deno fmt -'. This is useful for editor integrations, such as 'cat main.ts | deno fmt -'.
deno fmt --ignore flag
The --ignore flag excludes files from formatting. Multiple patterns can be specified, separated by commas, such as 'deno fmt --ignore=dist/,build/'.
deno fmt configuration precedence
Configuration precedence for deno fmt, from highest to lowest, is: 1) CLI flags (--indent-width, --use-tabs, and so on), 2) The fmt block in deno.json, 3) .editorconfig, 4) Built-in defaults. The .editorconfig file only supplies values not already configured through a flag or deno.json.
deno fmt .editorconfig property mapping
Properties in .editorconfig files map to deno fmt options as follows: indent_style maps to use-tabs, indent_size maps to indent-width, and max_line_length maps to line-width.
deno fmt supported file types
deno fmt supports the following file types and extensions: JavaScript (.js, .cjs, .mjs), TypeScript (.ts, .mts, .cts), JSX (.jsx), TSX (.tsx), Markdown (.md, .mkd, .mkdn, .mdwn, .mdown, .markdown), JSON (.json), JSONC (.jsonc), CSS (.css), HTML (.html), XML (.xml), SVG (.svg), Nunjucks (.njk), Vento (.vto), YAML (.yml, .yaml), SCSS (.scss), LESS (.less), Jupyter Notebook (.ipynb), Astro (.astro, requires --unstable-component flag or "unstable": ["fmt-component"] config), Svelte (.svelte, requires --unstable-component flag or "unstable": ["fmt-component"] config), Vue (.vue, requires --unstable-component flag or "unstable": ["fmt-component"] config), SQL (.sql, requires --unstable-sql flag or "unstable": ["fmt-sql"] config).
deno fmt markdown code snippet formatting
deno fmt can format code snippets in Markdown files. Snippets must be enclosed in triple backticks and have a language attribute.
deno fmt // deno-fmt-ignore-file comment
In JavaScript, TypeScript, and JSONC files, ignore formatting an entire file by adding a '// deno-fmt-ignore-file' comment at the top of the file.
deno fmt <!-- deno-fmt-ignore --> comment
In Markdown, HTML, and CSS files, ignore formatting the next item by preceding it with a '<!-- deno-fmt-ignore -->' comment.
deno fmt <!-- deno-fmt-ignore-start --> and <!-- deno-fmt-ignore-end --> comments
In Markdown, HTML, and CSS files, ignore formatting a section of code by surrounding it with '<!-- deno-fmt-ignore-start -->' and '<!-- deno-fmt-ignore-end -->' comments.
deno fmt <!-- deno-fmt-ignore-file --> comment
In Markdown, HTML, and CSS files, ignore formatting an entire file by adding a '<!-- deno-fmt-ignore-file -->' comment at the top of the file.
deno fmt # deno-fmt-ignore comment for YAML
In YAML files, ignore formatting the next item by preceding it with a '# deno-fmt-ignore' comment.
deno fmt markup and style formatter behavior
The markup formatters (HTML, XML, SVG, and unstable component formats) and the style formatters (CSS, SCSS, and Less) only adjust whitespace. They never reorder or rewrite tokens, and they pass unknown syntax (vendor extensions, future at-rules, template expressions, even broken markup) through unchanged instead of erroring, making formatting more robust on real-world files.
deno fmt --check in CI pipelines
Use `deno fmt --check` in CI pipelines to verify that code is formatted according to Deno's default formatting conventions without making changes.