# [Google Closure Compiler](https://developers.google.com/closure/compiler/)

[![Build Status](https://github.com/google/closure-compiler/workflows/Compiler%20CI/badge.svg)](https://github.com/google/closure-compiler/actions)
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The [Closure Compiler](https://developers.google.com/closure/compiler/) is a
tool for making JavaScript download and run faster. It is a true compiler for
JavaScript. Instead of compiling from a source language to machine code, it
compiles from JavaScript to better JavaScript. It parses your JavaScript,
analyzes it, removes dead code and rewrites and minimizes what's left. It also
checks syntax, variable references, and types, and warns about common JavaScript
pitfalls.

## Getting Started

*   Pre-compiled releases of the compiler are available via:
    -   [Maven](https://mvnrepository.com/artifact/com.google.javascript/closure-compiler)
    -   [NPM](https://www.npmjs.com/package/google-closure-compiler) - includes
        java, native and javascript versions.
*   See the
    [Google Developers Site](https://developers.google.com/closure/compiler/docs/gettingstarted_app)
    for documentation including instructions for running the compiler from the
    command line.

## Options for Getting Help

1.  Post in the
    [Closure Compiler Discuss Group](https://groups.google.com/forum/#!forum/closure-compiler-discuss).
1.  Ask a question on
    [Stack Overflow](https://stackoverflow.com/questions/tagged/google-closure-compiler).
1.  Consult the [FAQ](https://github.com/google/closure-compiler/wiki/FAQ).

## Building it Yourself

Note: The Closure Compiler requires [Java 8 or higher](https://www.java.com/).

### Using [Bazel](https://bazel.build/)

1.  Install
    [Bazelisk](https://docs.bazel.build/versions/master/install-bazelisk.html).

2.  On the command line, at the root of this project, run

    ```sh
    bazelisk build //:compiler_unshaded_deploy.jar
    ```

    This will produce a JAR called `bazel-bin/compiler_unshaded_deploy.jar`. You
    can run this JAR as per the [Running section](#running) of this Readme.

    If you want to integrate the compiler into a larger Java program, depend on
    `//:compiler_shaded_deploy.jar` instead.

### Using an IDE

See [Bazel IDE Integrations](https://docs.bazel.build/versions/master/ide.html)

## Running

On the command line, at the root of this project, type

```sh
bazel-bin/compiler_unshaded_deploy.jar
```

This starts the compiler in interactive mode. Type

```javascript
var x = 17 + 25;
```

then hit "Enter", then hit "Ctrl-Z" (on Windows) or "Ctrl-D" (on Mac or Linux)
and "Enter" again. The Compiler will respond:

```javascript
var x=42;
```

The Closure Compiler has many options for reading input from a file, writing
output to a file, checking your code, and running optimizations. To learn more,
type

```
java -jar compiler.jar --help
```

More detailed information about running the Closure Compiler is available in the
[documentation](https://developers.google.com/closure/compiler/docs/gettingstarted_app).

### Run using Eclipse

1.  Open the class `src/com/google/javascript/jscomp/CommandLineRunner.java` or
    create your own extended version of the class.
2.  Run the class in Eclipse.
3.  See the instructions above on how to use the interactive mode - but beware
    of the
    [bug](https://stackoverflow.com/questions/4711098/passing-end-of-transmission-ctrl-d-character-in-eclipse-cdt-console)
    regarding passing "End of Transmission" in the Eclipse console.

## Compiling Multiple Scripts

If you have multiple scripts, you should compile them all together with one
compile command.

```bash
java -jar compiler.jar --js_output_file=out.js in1.js in2.js in3.js ...
```

You can also use minimatch-style globs.

```bash
# Recursively include all js files in subdirs
java -jar compiler.jar --js_output_file=out.js 'src/**.js'

# Recursively include all js files in subdirs, excluding test files.
# Use single-quotes, so that bash doesn't try to expand the '!'
java -jar compiler.jar --js_output_file=out.js 'src/**.js' '!**_test.js'
```

The Closure Compiler will concatenate the files in the order they're passed at
the command line.

If you're using globs or many files, you may start to run into problems with
managing dependencies between scripts. In this case, you should use the
[Closure Library](https://developers.google.com/closure/library/). It contains
functions for enforcing dependencies between scripts, and Closure Compiler will
re-order the inputs automatically.

## How to Contribute

### Reporting a bug

1.  First make sure that it is really a bug and not simply the way that Closure
    Compiler works (especially true for ADVANCED_OPTIMIZATIONS).
    *   Check the
        [official documentation](https://developers.google.com/closure/compiler/)
    *   Consult the [FAQ](https://github.com/google/closure-compiler/wiki/FAQ)
    *   Search on
        [Stack Overflow](https://stackoverflow.com/questions/tagged/google-closure-compiler)
        and in the
        [Closure Compiler Discuss Group](https://groups.google.com/forum/#!forum/closure-compiler-discuss)
    *   Look through the list of
        [compiler assumptions](https://github.com/google/closure-compiler/wiki/Compiler-Assumptions).
2.  If you still think you have found a bug, make sure someone hasn't already
    reported it. See the list of
    [known issues](https://github.com/google/closure-compiler/issues).
3.  If it hasn't been reported yet, post a new issue. Make sure to add enough
    detail so that the bug can be recreated. The smaller the reproduction code,
    the better.

### Suggesting a Feature

1.  Consult the [FAQ](https://github.com/google/closure-compiler/wiki/FAQ) to
    make sure that the behaviour you would like isn't specifically excluded
    (such as string inlining).
2.  Make sure someone hasn't requested the same thing. See the list of
    [known issues](https://github.com/google/closure-compiler/issues).
3.  Read up on
    [what type of feature requests are accepted](https://github.com/google/closure-compiler/wiki/FAQ#how-do-i-submit-a-feature-request-for-a-new-type-of-optimization).
4.  Submit your request as an issue.

### Submitting patches

1.  All contributors must sign a contributor license agreement (CLA). A CLA
    basically says that you own the rights to any code you contribute, and that
    you give us permission to use that code in Closure Compiler. You maintain
    the copyright on that code. If you own all the rights to your code, you can
    fill out an
    [individual CLA](https://code.google.com/legal/individual-cla-v1.0.html). If
    your employer has any rights to your code, then they also need to fill out a
    [corporate CLA](https://code.google.com/legal/corporate-cla-v1.0.html). If
    you don't know if your employer has any rights to your code, you should ask
    before signing anything. By default, anyone with an @google.com email
    address already has a CLA signed for them.
2.  To make sure your changes are of the type that will be accepted, ask about
    your patch on the
    [Closure Compiler Discuss Group](https://groups.google.com/forum/#!forum/closure-compiler-discuss)
3.  Fork the repository.
4.  Make your changes. Check out our
    [coding conventions](https://github.com/google/closure-compiler/wiki/Contributors#coding-conventions)
    for details on making sure your code is in correct style.
5.  Submit a pull request for your changes. A project developer will review your
    work and then merge your request into the project.

## Closure Compiler License

Copyright 2009 The Closure Compiler Authors.

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.

## Dependency Licenses

### Rhino

<table>
  <tr>
    <td>Code Path</td>
    <td>
      <code>src/com/google/javascript/rhino</code>, <code>test/com/google/javascript/rhino</code>
    </td>
  </tr>

  <tr>
    <td>URL</td>
    <td>https://developer.mozilla.org/en-US/docs/Mozilla/Projects/Rhino</td>
  </tr>

  <tr>
    <td>Version</td>
    <td>1.5R3, with heavy modifications</td>
  </tr>

  <tr>
    <td>License</td>
    <td>Netscape Public License and MPL / GPL dual license</td>
  </tr>

  <tr>
    <td>Description</td>
    <td>A partial copy of Mozilla Rhino. Mozilla Rhino is an
implementation of JavaScript for the JVM.  The JavaScript
parse tree data structures were extracted and modified
significantly for use by Google's JavaScript compiler.</td>
  </tr>

  <tr>
    <td>Local Modifications</td>
    <td>The packages have been renamespaced. All code not
relevant to the parse tree has been removed. A JsDoc parser and static typing
system have been added.</td>
  </tr>
</table>

### Args4j

<table>
  <tr>
    <td>URL</td>
    <td>http://args4j.kohsuke.org/</td>
  </tr>

  <tr>
    <td>Version</td>
    <td>2.33</td>
  </tr>

  <tr>
    <td>License</td>
    <td>MIT</td>
  </tr>

  <tr>
    <td>Description</td>
    <td>args4j is a small Java class library that makes it easy to parse command line
options/arguments in your CUI application.</td>
  </tr>

  <tr>
    <td>Local Modifications</td>
    <td>None</td>
  </tr>
</table>

### Guava Libraries

<table>
  <tr>
    <td>URL</td>
    <td>https://github.com/google/guava</td>
  </tr>

  <tr>
    <td>Version</td>
    <td>20.0</td>
  </tr>

  <tr>
    <td>License</td>
    <td>Apache License 2.0</td>
  </tr>

  <tr>
    <td>Description</td>
    <td>Google's core Java libraries.</td>
  </tr>

  <tr>
    <td>Local Modifications</td>
    <td>None</td>
  </tr>
</table>

### JSR 305

<table>
  <tr>
    <td>URL</td>
    <td>https://github.com/findbugsproject/findbugs</td>
  </tr>

  <tr>
    <td>Version</td>
    <td>3.0.1</td>
  </tr>

  <tr>
    <td>License</td>
    <td>BSD License</td>
  </tr>

  <tr>
    <td>Description</td>
    <td>Annotations for software defect detection.</td>
  </tr>

  <tr>
    <td>Local Modifications</td>
    <td>None</td>
  </tr>
</table>

### JUnit

<table>
  <tr>
    <td>URL</td>
    <td>http://junit.org/junit4/</td>
  </tr>

  <tr>
    <td>Version</td>
    <td>4.12</td>
  </tr>

  <tr>
    <td>License</td>
    <td>Common Public License 1.0</td>
  </tr>

  <tr>
    <td>Description</td>
    <td>A framework for writing and running automated tests in Java.</td>
  </tr>

  <tr>
    <td>Local Modifications</td>
    <td>None</td>
  </tr>
</table>

### Protocol Buffers

<table>
  <tr>
    <td>URL</td>
    <td>https://github.com/google/protobuf</td>
  </tr>

  <tr>
    <td>Version</td>
    <td>3.0.2</td>
  </tr>

  <tr>
    <td>License</td>
    <td>New BSD License</td>
  </tr>

  <tr>
    <td>Description</td>
    <td>Supporting libraries for protocol buffers,
an encoding of structured data.</td>
  </tr>

  <tr>
    <td>Local Modifications</td>
    <td>None</td>
  </tr>
</table>

### RE2/J

<table>
  <tr>
    <td>URL</td>
    <td>https://github.com/google/re2j</td>
  </tr>

  <tr>
    <td>Version</td>
    <td>1.3</td>
  </tr>

  <tr>
    <td>License</td>
    <td>New BSD License</td>
  </tr>

  <tr>
    <td>Description</td>
    <td>Linear time regular expression matching in Java.</td>
  </tr>

  <tr>
    <td>Local Modifications</td>
    <td>None</td>
  </tr>
</table>

### Truth

<table>
  <tr>
    <td>URL</td>
    <td>https://github.com/google/truth</td>
  </tr>

  <tr>
    <td>Version</td>
    <td>0.32</td>
  </tr>

  <tr>
    <td>License</td>
    <td>Apache License 2.0</td>
  </tr>

  <tr>
    <td>Description</td>
    <td>Assertion/Proposition framework for Java unit tests</td>
  </tr>

  <tr>
    <td>Local Modifications</td>
    <td>None</td>
  </tr>
</table>

### Ant

<table>
  <tr>
    <td>URL</td>
    <td>https://ant.apache.org/bindownload.cgi</td>
  </tr>

  <tr>
    <td>Version</td>
    <td>1.9.7</td>
  </tr>

  <tr>
    <td>License</td>
    <td>Apache License 2.0</td>
  </tr>

  <tr>
    <td>Description</td>
    <td>Ant is a Java based build tool. In theory it is kind of like "make"
without make's wrinkles and with the full portability of pure java code.</td>
  </tr>

  <tr>
    <td>Local Modifications</td>
    <td>None</td>
  </tr>
</table>

### GSON

<table>
  <tr>
    <td>URL</td>
    <td>https://github.com/google/gson</td>
  </tr>

  <tr>
    <td>Version</td>
    <td>2.7</td>
  </tr>

  <tr>
    <td>License</td>
    <td>Apache license 2.0</td>
  </tr>

  <tr>
    <td>Description</td>
    <td>A Java library to convert JSON to Java objects and vice-versa</td>
  </tr>

  <tr>
    <td>Local Modifications</td>
    <td>None</td>
  </tr>
</table>

### Node.js Closure Compiler Externs

<table>
  <tr>
    <td>Code Path</td>
    <td><code>contrib/nodejs</code></td>
  </tr>

  <tr>
    <td>URL</td>
    <td>https://github.com/dcodeIO/node.js-closure-compiler-externs</td>
  </tr>

  <tr>
    <td>Version</td>
    <td>e891b4fbcf5f466cc4307b0fa842a7d8163a073a</td>
  </tr>

  <tr>
    <td>License</td>
    <td>Apache 2.0 license</td>
  </tr>

  <tr>
    <td>Description</td>
    <td>Type contracts for NodeJS APIs</td>
  </tr>

  <tr>
    <td>Local Modifications</td>
    <td>Substantial changes to make them compatible with NpmCommandLineRunner.</td>
  </tr>
</table>