6.0 KiB
id | title |
---|---|
usage | Usage |
Install
yarn add prettier --dev
You can install it globally if you like:
yarn global add prettier
We're using yarn
but you can use npm
if you like:
npm install [--save-dev|--global] prettier
CLI
Run Prettier through the CLI with this script. Run it without any arguments to see the options.
To format a file in-place, use --write
. You may want to consider
committing your code before doing that, just in case.
prettier [opts] [filename ...]
In practice, this may look something like:
prettier --single-quote --trailing-comma es5 --write "{app,__{tests,mocks}__}/**/*.js"
Don't forget the quotes around the globs! The quotes make sure that Prettier expands the globs rather than your shell, for cross-platform usage. The glob syntax from the glob module is used.
Prettier CLI will ignore files located in node_modules
directory. To opt-out from this behavior use --with-node-modules
flag.
If you're worried that Prettier will change the correctness of your code, add --debug-check
to the command.
This will cause Prettier to print an error message if it detects that code correctness might have changed.
Note that --write
cannot be used with --debug-check
.
Another useful flag is --list-different
(or -l
) which prints the filenames of files that are different from Prettier formatting. If there are differences the script errors out, which is useful in a CI scenario.
prettier --single-quote --list-different "src/**/*.js"
ESLint
If you are using ESLint, integrating Prettier to your workflow is straightforward:
Just add Prettier as an ESLint rule using eslint-plugin-prettier.
yarn add --dev prettier eslint-plugin-prettier
// .eslintrc.json
{
"plugins": [
"prettier"
],
"rules": {
"prettier/prettier": "error"
}
}
We also recommend that you use eslint-config-prettier to disable all the existing formatting rules. It's a one liner that can be added on-top of any existing ESLint configuration.
$ yarn add --dev eslint-config-prettier
.eslintrc.json:
{
"extends": [
"prettier"
]
}
Pre-commit Hook
You can use Prettier with a pre-commit tool. This can re-format your files that are marked as "staged" via git add
before you commit.
Option 1. lint-staged
Install it along with husky:
yarn add lint-staged husky --dev
and add this config to your package.json
:
{
"scripts": {
"precommit": "lint-staged"
},
"lint-staged": {
"*.js": [
"prettier --write",
"git add"
]
}
}
See https://github.com/okonet/lint-staged#configuration for more details about how you can configure lint-staged.
Option 2. pre-commit
Copy the following config into your .pre-commit-config.yaml
file:
- repo: https://github.com/prettier/prettier
sha: '' # Use the sha or tag you want to point at
hooks:
- id: prettier
Find more info from here.
Option 3. bash script
Alternately you can save this script as .git/hooks/pre-commit
and give it execute permission:
#!/bin/sh
jsfiles=$(git diff --cached --name-only --diff-filter=ACM | grep '\.jsx\?$' | tr '\n' ' ')
[ -z "$jsfiles" ] && exit 0
# Prettify all staged .js files
echo "$jsfiles" | xargs ./node_modules/.bin/prettier --write
# Add back the modified/prettified files to staging
echo "$jsfiles" | xargs git add
exit 0
API
The API has three functions: format
, check
, and formatWithCursor
.
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 });
// -> "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 --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 });
// -> { formatted: '1;\n', cursorOffset: 1 }
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, { babylon }) {
const ast = babylon(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.
Excluding code from formatting
A JavaScript comment of // prettier-ignore
will exclude the next node in the abstract syntax tree from formatting.
For example:
matrix(
1, 0, 0,
0, 1, 0,
0, 0, 1
)
// prettier-ignore
matrix(
1, 0, 0,
0, 1, 0,
0, 0, 1
)
will be transformed to:
matrix(1, 0, 0, 0, 1, 0, 0, 0, 1);
// prettier-ignore
matrix(
1, 0, 0,
0, 1, 0,
0, 0, 1
)