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:
- 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 8 or higher.
Maven
Using-
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 thecom.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.
Eclipse
Using- Download and open Eclipse IDE. Disable
Project > Build automatically
during this process. - On the command line, at the root of this project, run
mvn eclipse:eclipse -DdownloadSources=true
to download JARs and build Eclipse project configuration. - Run
mvn clean
andmvn -DskipTests
to ensure AutoValues are generated and updated. - In Eclipse, navigate to
File > Import > Maven > Existing Maven Projects
and browse to closure-compiler. - Import both closure-compiler and the nested externs project.
- Disregard the warnings about maven-antrun-plugin and build errors.
- Configure the project to use the Google Eclipse style guide
- Edit
.classpath
in closure-compiler-parent. Delete the<classpathentry ... kind="src" path="src" ... />
line, then add:<classpathentry excluding="com/google/debugging/sourcemap/super/**|com/google/javascript/jscomp/debugger/gwt/DebuggerGwtMain.java|com/google/javascript/jscomp/gwt/|com/google/javascript/jscomp/resources/super-gwt/**" kind="src" path="src"/> <classpathentry kind="src" path="target/generated-sources/annotations"/>
- Ensure the Eclipse project settings specify 1.8 compliance level in "Java Compiler".
- Build project in Eclipse (right click on the project
closure-compiler-parent
and selectBuild 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
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
Code Path |
src/com/google/javascript/rhino , test/com/google/javascript/rhino
|
URL | https://developer.mozilla.org/en-US/docs/Mozilla/Projects/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 | http://args4j.kohsuke.org/ |
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://junit.org/junit4/ |
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 | 0.32 |
License | Apache License 2.0 |
Description | Assertion/Proposition framework for Java unit tests |
Local Modifications | None |
Ant
URL | https://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. |