我无法使用Google Closure Compiler编译一个包含let关键字的简单Javascript代码。
我的Javascript文件example.js：
function display() {
let a = 'hello';
console.log( a, 'world' );
}
display();
我编译的JAVA代码是：
package compiler;
import static com.google.javascript.jscomp.SourceFile.fromCode;
import static com.google.javascript.jscomp.SourceFile.fromInputStream;
import static java.nio.charset.Charset.defaultCharset;
import java.io.IOException;
import java.io.InputStream;
import java.net.URI;
import java.net.URISyntaxException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.stream.Collectors;
import com.google.javascript.jscomp.CompilationLevel;
import com.google.javascript.jscomp.Compiler;
import com.google.javascript.jscomp.CompilerOptions;
import com.google.javascript.jscomp.CompilerOptions.LanguageMode;
import com.google.javascript.jscomp.JSError;
import com.google.javascript.jscomp.Result;
import com.google.javascript.jscomp.SourceFile;
public class CompilerMain {
public static void main(String[] args) throws URISyntaxException, IOException {
final String script = readScript();
final Compiler compiler = new Compiler();
final CompilerOptions options = new CompilerOptions();
// CompilationLevel.SIMPLE_OPTIMIZATIONS.setOptionsForCompilationLevel(options);
CompilationLevel.ADVANCED_OPTIMIZATIONS.setOptionsForCompilationLevel(options);
options.setContinueAfterErrors(true);
options.setLanguageIn(LanguageMode.ECMASCRIPT6);
options.setLanguageOut(LanguageMode.ECMASCRIPT5);
options.setExternExports(true);
System.out.println("Compiling:\n" + script);
System.out.println("------------------------------");
final List<SourceFile> externs = new ArrayList<>();
externs.add( externSourceFileES6("base.js"));
externs.add( externSourceFileES6("es6_runtime.js"));
// externs.add( externSourceFileES6("runtime_type_check.js"));
final List<SourceFile> inputs = new ArrayList<>();
final SourceFile src = fromCode("stdin.txt", script);
inputs.add(src);
final Result result = compiler.compile(externs, inputs, options);
System.out.println("------------------------------");
final JSError[] errors = result.errors;
if (errors.length > 0) {
for (JSError error : errors) {
System.err.println(error.toString());
}
} else {
System.out.println(compiler.toSource());
}
}
private static SourceFile externSourceFileES6(final String filename) throws IOException {
final InputStream inputstream = CompilerMain.class
.getResourceAsStream("/com/google/javascript/jscomp/js/" + filename);
return fromInputStream(filename, inputstream, defaultCharset());
}
private static String readScript() throws URISyntaxException, IOException {
final URI uri = CompilerMain.class.getResource("/compiler/example1.js").toURI();
final Path path = Paths.get(uri);
return Files.readAllLines(path).stream().collect(Collectors.joining("\n"));
}
}
输出结果为：
Compiling:
function display() {
let a = 'hello';
console.log( a, 'world' );
}
display();
------------------------------
mars 22, 2017 4:48:02 PM com.google.javascript.jscomp.LoggerErrorManager println
GRAVE: ERROR - Missing externs definition for Symbol. Did you forget to include the ES6 externs?
mars 22, 2017 4:48:02 PM com.google.javascript.jscomp.LoggerErrorManager printSummary
AVERTISSEMENT: 1 error(s), 0 warning(s), 75.0% typed
------------------------------
JSC_MISSING_ES6_EXTERNS. Missing externs definition for Symbol. Did you forget to include the ES6 externs? at (unknown source) line (unknown line) : (unknown column)
Maven依赖可能对您有所帮助：
<dependency>
<groupId>com.google.javascript</groupId>
<artifactId>closure-compiler</artifactId>
<version>v20170124</version>
</dependency>
请告知