Google Closure Compiler

The 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

Download the latest version (Release details here)
Download a specific version. Also available via:
- Maven
- NPM
Use the JavaScript version, with no Java dependency
See the Google Developers Site for documentation including instructions for running the compiler from the command line.

Options for Getting Help

Post in the Closure Compiler Discuss Group.
Ask a question on Stack Overflow.
Consult the FAQ.

Building it Yourself

Note: The Closure Compiler requires Java 7 or higher.

Using Maven

Download Maven.

Add sonatype snapshots repository to ~/.m2/settings.xml:

<profile>
  <id>allow-snapshots</id>
     <activation><activeByDefault>true</activeByDefault></activation>
  <repositories>
    <repository>
      <id>snapshots-repo</id>
      <url>https://oss.sonatype.org/content/repositories/snapshots</url>
      <releases><enabled>false</enabled></releases>
      <snapshots><enabled>true</enabled></snapshots>
    </repository>
  </repositories>
</profile>

On the command line, at the root of this project, run mvn -DskipTests (omit the -DskipTests if you want to run all the unit tests too).

This will produce a jar file called target/closure-compiler-1.0-SNAPSHOT.jar. You can run this jar as per the Running section of this Readme. If you want to depend on the compiler via Maven in another Java project, use the com.google.javascript/closure-compiler-unshaded artifact.

Running mvn -DskipTests -pl externs/pom.xml,pom-main.xml,pom-main-shaded.xml will skip building the GWT version of the compiler. This can speed up the build process significantly.

Using Eclipse

Download and open the Eclipse IDE.
On the command line, at the root of this project, run mvn eclipse:eclipse -DdownloadSources=true to download JARs and build Eclipse project configuration.
Navigate to File > Import > Maven > Existing Maven Projects and browse to closure-compiler inside of Eclipse.
Import both closure-compiler and the nested externs project.
Disregard the warnings about maven-antrun-plugin and build errors.
In Package Explorer, remove from the build path:
- src/com/google/javascript/jscomp/debugger/DebuggerGwtMain.java
- src/com/google/javascript/jscomp/gwt/
Exclude the files in the directory src/com/google/debugging/sourcemap/super from the project.
Build project in Eclipse (right click on the project closure-compiler-parent and select Build Project).
See Using Maven above to build the JAR.

Running

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

java -jar target/closure-compiler-1.0-SNAPSHOT.jar

This starts the compiler in interactive mode. Type

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:

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.

Run using Eclipse

Open the class src/com/google/javascript/jscomp/CommandLineRunner.java or create your own extended version of the class.
Run the class in Eclipse.
See the instructions above on how to use the interactive mode - but beware of the bug 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.

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

You can also use minimatch-style globs.

# 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. It contains functions for enforcing dependencies between scripts, and Closure Compiler will re-order the inputs automatically.

How to Contribute

Reporting a bug

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
Consult the FAQ
Search on Stack Overflow and in the Closure Compiler Discuss Group

If you still think you have found a bug, make sure someone hasn't already reported it. See the list of known issues.
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

Consult the FAQ to make sure that the behaviour you would like isn't specifically excluded (such as string inlining).
Make sure someone hasn't requested the same thing. See the list of known issues.
Read up on what type of feature requests are accepted.
Submit your request as an issue.

Submitting patches

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. If your employer has any rights to your code, then they also need to fill out a corporate CLA. 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.
To make sure your changes are of the type that will be accepted, ask about your patch on the Closure Compiler Discuss Group
Fork the repository.
Make your changes. Check out our coding conventions for details on making sure your code is in correct style.
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

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

Code Path	`src/com/google/javascript/rhino`, `test/com/google/javascript/rhino`
URL	http://www.mozilla.org/rhino
Version	1.5R3, with heavy modifications
License	Netscape Public License and MPL / GPL dual license
Description	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.
Local Modifications	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.

Args4j

URL	https://args4j.dev.java.net/
Version	2.33
License	MIT
Description	args4j is a small Java class library that makes it easy to parse command line options/arguments in your CUI application.
Local Modifications	None

Guava Libraries

URL	https://github.com/google/guava
Version	20.0
License	Apache License 2.0
Description	Google's core Java libraries.
Local Modifications	None

JSR 305

URL	https://github.com/findbugsproject/findbugs
Version	3.0.1
License	BSD License
Description	Annotations for software defect detection.
Local Modifications	None

JUnit

URL	http://sourceforge.net/projects/junit/
Version	4.12
License	Common Public License 1.0
Description	A framework for writing and running automated tests in Java.
Local Modifications	None

Protocol Buffers

URL	https://github.com/google/protobuf
Version	3.0.2
License	New BSD License
Description	Supporting libraries for protocol buffers, an encoding of structured data.
Local Modifications	None

Truth

URL	https://github.com/google/truth
Version	0.30
License	Apache License 2.0
Description	Assertion/Proposition framework for Java unit tests
Local Modifications	None

Ant

URL	http://ant.apache.org/bindownload.cgi
Version	1.9.7
License	Apache License 2.0
Description	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.
Local Modifications	None

GSON

URL	https://github.com/google/gson
Version	2.7
License	Apache license 2.0
Description	A Java library to convert JSON to Java objects and vice-versa
Local Modifications	None

Node.js Closure Compiler Externs

Code Path	`contrib/nodejs`
URL	https://github.com/dcodeIO/node.js-closure-compiler-externs
Version	e891b4fbcf5f466cc4307b0fa842a7d8163a073a
License	Apache 2.0 license
Description	Type contracts for NodeJS APIs
Local Modifications	Substantial changes to make them compatible with NpmCommandLineRunner.

drewinglis/closure-compiler