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.
The easiest way to install the compiler is with NPM or Yarn:
yarn global add google-closure-compiler
# OR
npm i -g google-closure-compiler
The package manager will link the binary for you, and you can access the compiler with:
google-closure-compiler
This starts the compiler in interactive mode. Type:
var x = 17 + 25;
Hit Enter
, then Ctrl+Z
(on Windows) or Ctrl+D
(on Mac/Linux), then Enter
again. The Compiler will respond with the compiled output (using SIMPLE
mode by default):
var x=42;
A pre-compiled release of the compiler is also available via Maven.
The Closure Compiler has many options for reading input from a file, writing output to a file, checking your code, and running optimizations. Here is a simple example of compressing a JS program:
google-closure-compiler --js file.js --js_output_file file.out.js
We get the most benefit from the compiler if we give it all of our source code (see Compiling Multiple Scripts), which allows us to use ADVANCED
optimizations:
google-closure-compiler -O ADVANCED rollup.js --js_output_file rollup.min.js
NOTE: The output below is just an example and not kept up-to-date. The Flags and Options wiki page is updated during each release.
To see all of the compiler's options, type:
google-closure-compiler --help
--flag | Description |
---|---|
--compilation_level (-O) | Specifies the compilation level to use. Options: BUNDLE , WHITESPACE_ONLY , SIMPLE (default), ADVANCED |
--env | Determines the set of builtin externs to load. Options: BROWSER , CUSTOM . Defaults to BROWSER . |
--externs | The file containing JavaScript externs. You may specify multiple |
--js | The JavaScript filename. You may specify multiple. The flag name is optional, because args are interpreted as files by default. You may also use minimatch-style glob patterns. For example, use --js='**.js' --js='!**_test.js' to recursively include all js files that do not end in _test.js |
--js_output_file | Primary output filename. If not specified, output is written to stdout. |
--language_in | Sets the language spec to which input sources should conform. Options: ECMASCRIPT3 , ECMASCRIPT5 , ECMASCRIPT5_STRICT , ECMASCRIPT_2015 , ECMASCRIPT_2016 , ECMASCRIPT_2017 , ECMASCRIPT_2018 , ECMASCRIPT_2019 , STABLE , ECMASCRIPT_NEXT |
--language_out | Sets the language spec to which output should conform. Options: ECMASCRIPT3 , ECMASCRIPT5 , ECMASCRIPT5_STRICT , ECMASCRIPT_2015 , ECMASCRIPT_2016 , ECMASCRIPT_2017 , ECMASCRIPT_2018 , ECMASCRIPT_2019 , STABLE |
--warning_level (-W) | Specifies the warning level to use. Options: QUIET , DEFAULT , VERBOSE |
You can access the compiler in a JS program by importing google-closure-compiler
:
import closureCompiler from 'google-closure-compiler';
const { compiler } = closureCompiler;
new compiler({
js: 'file-one.js',
compilation_level: 'ADVANCED'
});
This package will provide programmatic access to the native Graal binary in most cases, and will fall back to the Java version otherwise.
If you have multiple scripts, you should compile them all together with one compile command.
google-closure-compiler in1.js in2.js in3.js --js_output_file out.js
You can also use minimatch-style globs.
# Recursively include all js files in subdirs
google-closure-compiler 'src/**.js' --js_output_file out.js
# Recursively include all js files in subdirs, excluding test files.
# Use single-quotes, so that bash doesn't try to expand the '!'
google-closure-compiler 'src/**.js' '!**_test.js' --js_output_file out.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.
To build the compiler yourself, you will need the following:
Prerequisite | Description |
---|---|
Java 11 or later | Used to compile the compiler's source code. |
Git | Used by Bazel to download dependencies. |
Bazelisk | Used to build the various compiler targets. |
Bazelisk is a wrapper around Bazel that dynamically loads the appropriate version of Bazel for a given repository. Using it prevents spurious errors that result from using the wrong version of Bazel to build the compiler, as well as makes it easy to use different Bazel versions for other projects.
Bazelisk is available through many package managers. Feel free to use whichever you're most comfortable with.
Instructions for installing Bazelisk.
$ bazelisk build //:compiler_uberjar_deploy.jar
# OR to build everything
$ bazelisk build //:all
Tests can be executed in a similar way. The following command will run all tests in the repo.
$ bazelisk test //:all
There are hundreds of individual test targets, so it will take a few minutes to run all of them. While developing, it's usually better to specify the exact tests you're interested in.
bazelisk test //:$path_to_test_file
See Bazel IDE Integrations.
Once the compiler has been built, the compiled JAR will be in the bazel-bin/
directory. You can access it with a call to java -jar ...
or by using the package.json script:
# java -jar bazel-bin/compiler_uberjar_deploy.jar [...args]
yarn compile [...args]
src/com/google/javascript/jscomp/CommandLineRunner.java
or create your own extended version of the class.However you choose to contribute, please abide by our code of conduct to keep our community a healthy and welcoming place.
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.
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. |
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 |
URL | https://github.com/google/guava |
Version | 31.0.1 |
License | Apache License 2.0 |
Description | Google's core Java libraries. |
Local Modifications | None |
URL | https://github.com/findbugsproject/findbugs |
Version | 3.0.1 |
License | BSD License |
Description | Annotations for software defect detection. |
Local Modifications | None |
URL | http://junit.org/junit4/ |
Version | 4.13 |
License | Common Public License 1.0 |
Description | A framework for writing and running automated tests in Java. |
Local Modifications | None |
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 |
URL | https://github.com/google/re2j |
Version | 1.3 |
License | New BSD License |
Description | Linear time regular expression matching in Java. |
Local Modifications | None |
URL | https://github.com/google/truth |
Version | 1.1 |
License | Apache License 2.0 |
Description | Assertion/Proposition framework for Java unit tests |
Local Modifications | None |
URL | https://ant.apache.org/bindownload.cgi |
Version | 1.10.11 |
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 |
URL | https://github.com/google/gson |
Version | 2.9.1 |
License | Apache license 2.0 |
Description | A Java library to convert JSON to Java objects and vice-versa |
Local Modifications | None |
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. |
Download Details:
Author: google
Official Github: https://github.com/google/closure-compiler
License: Apache-2.0 license