Question

const prettier = require("prettier");

prettier.format(source [, options])

format is used to format text using Prettier. Options may be provided to override the defaults.

prettier.format("foo ( );", { semi: false, parser: "babel" });
// -> "foo()"

prettier.check(source [, options])

check checks to see if the file has been formatted with Prettier given those options and returns a Boolean. This is similar to the --check or --list-different parameter in the CLI and is useful for running Prettier in CI scenarios.

prettier.formatWithCursor(source [, options])

formatWithCursor both formats the code, and translates a cursor position from unformatted code to formatted code. This is useful for editor integrations, to prevent the cursor from moving when code is formatted.

The cursorOffset option should be provided, to specify where the cursor is. This option cannot be used with rangeStart and rangeEnd.

prettier.formatWithCursor(" 1", { cursorOffset: 2, parser: "babel" });
// -> { formatted: '1;\n', cursorOffset: 1 }

prettier.resolveConfig(filePath [, options])

resolveConfig can be used to resolve configuration for a given source file, passing its path as the first argument. The config search will start at the file path and continue to search up the directory (you can use process.cwd() to start searching from the current directory). Or you can pass directly the path of the config file as options.config if you don't wish to search for it. A promise is returned which will resolve to:

• An options object, providing a config file was found.
• null, if no file was found.

The promise will be rejected if there was an error parsing the configuration file.

If options.useCache is false, all caching will be bypassed.

const text = fs.readFileSync(filePath, "utf8");
prettier.resolveConfig(filePath).then(options => {
  const formatted = prettier.format(text, options);
});

If options.editorconfig is true and an .editorconfig file is in your project, Prettier will parse it and convert its properties to the corresponding prettier configuration. This configuration will be overridden by .prettierrc, etc. Currently, the following EditorConfig properties are supported:

• end_of_line
• indent_style
• indent_size/tab_width
• max_line_length

Use prettier.resolveConfig.sync(filePath [, options]) if you'd like to use sync version.

prettier.resolveConfigFile([filePath])

resolveConfigFile can be used to find the path of the Prettier configuration file that will be used when resolving the config (i.e. when calling resolveConfig). A promise is returned which will resolve to:

• The path of the configuration file.
• null, if no file was found.

The promise will be rejected if there was an error parsing the configuration file.

The search starts at process.cwd(), or at filePath if provided. Please see the cosmiconfig docs for details on how the resolving works.

prettier.resolveConfigFile().then(filePath => {
  prettier.resolveConfig(filePath).then(options => {
    const formatted = prettier.format(text, options);
  });
});

Use prettier.resolveConfigFile.sync([filePath]) if you'd like to use sync version.

prettier.clearConfigCache()

As you repeatedly call resolveConfig, the file system structure will be cached for performance. This function will clear the cache. Generally this is only needed for editor integrations that know that the file system has changed since the last format took place.

prettier.getFileInfo(filePath [, options])

getFileInfo can be used by editor extensions to decide if a particular file needs to be formatted. This method returns a promise, which resolves to an object with the following properties:

{
  ignored: boolean,
  inferredParser: string | null,
}

The promise will be rejected if the type of filePath is not string.

Setting options.ignorePath (string) and options.withNodeModules (boolean) influence the value of ignored (false by default).

Providing plugin paths in options.plugins (string[]) helps extract inferredParser for files that are not supported by Prettier core.

When setting options.resolveConfig (boolean, default false), Prettier will resolve the configuration for the given filePath. This is useful, for example, when the inferredParser might be overridden for a subset of files.

Use prettier.getFileInfo.sync(filePath [, options]) if you'd like to use sync version.

prettier.getSupportInfo([version])

Returns an object representing the parsers, languages and file types Prettier supports.

If version is provided (e.g. "1.5.0"), information for that version will be returned, otherwise information for the current version will be returned.

The support information looks like this:

{
  languages: Array<{
    name: string,
    since?: string,
    parsers: string[],
    group?: string,
    tmScope?: string,
    aceMode?: string,
    codemirrorMode?: string,
    codemirrorMimeType?: string,
    aliases?: string[],
    extensions?: string[],
    filenames?: string[],
    linguistLanguageId?: number,
    vscodeLanguageIds?: string[],
  }>
}

Custom Parser API

If you need to make modifications to the AST (such as codemods), or you want to provide an alternate parser, you can do so by setting the parser option to a function. The function signature of the parser function is:

(text: string, parsers: object, options: object) => AST;

Prettier's built-in parsers are exposed as properties on the parsers argument.

prettier.format("lodash ( )", {
  parser(text, { babel }) {
    const ast = babel(text);
    ast.program.body[0].expression.callee.name = "_";
    return ast;
  }
});
// -> "_();\n"

The --parser CLI option may be a path to a node.js module exporting a parse function.