jsfmt

jsfmt formats javascript and allows AST searching and rewriting. Analogous to gofmt.

Installation

npm install -g jsfmt

Why

Javascript formatters exist but most (all?) work on just strings, not the AST. Using Esprima under the hood we have access to the full AST and can do useful things like intelligent find and replace as in gofmt.

Usage

jsfmt [flags] [path ...]
  Action:
  --format=false, -f=false: format the input javascript
  --search="", -s="": search rule (e.g., 'a.slice')
  --rewrite="", -r="": rewrite rule (e.g., 'a.slice(b, len(a) -> a.slice(b)')

  Output (default is stdout):
  --list=false, -l=false: list files whose formatting differs from jsfmt's
  --diff=false, -d=false: display diffs instead of rewriting files
  --write=false, -w=false: write result to (source) file instead of stdout

  Config:
  --comments=true, -c=true: include comments in result

At least one action is required. If no path is given it will read from stdin. A directory path will recurse over all *.js files in the directory.

.jsfmtrc

Any of the esformatter formatting options can be overwritten via a .jsfmtrc file. The file is parsed using rc, which accepts either a json or ini formatted file.

jsfmt will also attempt to pickup and use the configured indent variable from your .jshintrc configuration file, if present.

Rewriting

The rewrite rule allows rewriting portions of the javascript's AST before formatting. This is especially handy for intelligent renaming and handling API changes from a library. The --rewrite flag must be a string of the form:

pattern -> replacement

Both pattern and replacement must be valid javascript. In pattern, single-character lowercase identifiers serve as wildcards matching arbitrary expressions; those expressions will be substituted for the same identifiers in the replacement.

Searching

The search rule is very similar but just outputs expressions that match the given search expression.

API

Searching:

var jsfmt = require('jsfmt');
var fs = require('fs');

var js = fs.readFileSync('my_file.js');

jsfmt.search(js, "R.Component.create(a, { dependencies: z })").forEach(function(matches, wildcards) {
  console.log(wildcards.z);
});

Rewriting:

var jsfmt = require('jsfmt');
var fs = require('fs');

var js = fs.readFileSync('my_file.js');

js = jsfmt.rewrite(js, "_.each(a, b) -> a.forEach(b)");

Examples

Rewrite occurences of _.reduce to use native reduce:

jsfmt --rewrite "_.reduce(a, b, c) -> a.reduce(b, c)" examples/reduce.js

Before:

var values = [1, 2, 3, 4];
_.reduce(values, function(sum, value) {
  return sum + value;
}, 0);

After:

var values = [1, 2, 3, 4];
values.reduce(function(sum, value) {
  return sum + value;
}, 0);

Changelog

v0.2.0

• Add rc and --config config.json support for formatting configuration
• Making --format the default action
• Fix support for shebang at the top of js files, e.g. #!/usr/bin/env node
• Fix jsfmt diff mode where whitespace was unaccounted for due to -b git diff option

v0.1.1

• Initial release

License

Copyright 2014 Rdio, Inc.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.