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Question

我想使用 Closure Compiler 来缩小/压缩 JS 代码。

问题是它没有像我期望的那样缩小。考虑下面的代码。当我传递字符串时

var func = function ( someArgument ) {
  alert ( someArgument ); 
  return someArgument; 
}

我希望缩小后的代码将“someArgument”重命名为更短的名称，例如“a”。

是这样还是我做错了什么？ TIA

public static void Compress( String src ) {

    ByteArrayOutputStream err = new ByteArrayOutputStream();

    CompilerOptions opt = new CompilerOptions();

    CompilationLevel.ADVANCED_OPTIMIZATIONS.setDebugOptionsForCompilationLevel( opt );

    Compiler.setLoggingLevel( Level.OFF );
    Compiler compiler = new Compiler( new PrintStream( err ) );
    compiler.disableThreads();

    List<SourceFile> externs = Collections.emptyList();
    List<SourceFile> inputs = Arrays.asList( SourceFile.fromCode( "javascript-code.js", src) );

    Result result = compiler.compile( externs, inputs, opt );

    System.out.println( "source: " + compiler.toSource() );
}

Answer 1

你正在使用setDebugOptionsForCompilationLevel()，你想要setOptionsForCompilationLevel()。来自the Source 这就是setDebugOptionsForCompilationLevel 正在做的事情：

public void setDebugOptionsForCompilationLevel(CompilerOptions options) {
    options.anonymousFunctionNaming = AnonymousFunctionNamingPolicy.UNMAPPED;
    options.generatePseudoNames = true;
    options.removeClosureAsserts = false;
    // Don't shadow variables as it is too confusing.
    options.shadowVariables = false;
}

虽然这是setOptionsForCompilationLevel() 正在做的事情：

// All the safe optimizations.
options.dependencyOptions.setDependencySorting(true);
options.closurePass = true;
options.foldConstants = true;
options.coalesceVariableNames = true;
options.deadAssignmentElimination = true;
options.extractPrototypeMemberDeclarations = true;
options.collapseVariableDeclarations = true;
options.convertToDottedProperties = true;
options.rewriteFunctionExpressions = true;
options.labelRenaming = true;
options.removeDeadCode = true;
options.optimizeArgumentsArray = true;
options.collapseObjectLiterals = true;
options.protectHiddenSideEffects = true;

// All the advance optimizations.
options.removeClosureAsserts = true;
options.aliasKeywords = true;
options.reserveRawExports = true;
options.setRenamingPolicy(
    VariableRenamingPolicy.ALL, PropertyRenamingPolicy.ALL_UNQUOTED);
options.shadowVariables = true;
options.removeUnusedPrototypeProperties = true;
options.removeUnusedPrototypePropertiesInExterns = true;
options.collapseAnonymousFunctions = true;
options.collapseProperties = true;
options.checkGlobalThisLevel = CheckLevel.WARNING;
options.rewriteFunctionExpressions = true;
options.smartNameRemoval = true;
options.inlineConstantVars = true;
options.setInlineFunctions(Reach.ALL);
options.inlineGetters = true;
options.setInlineVariables(Reach.ALL);
options.flowSensitiveInlineVariables = true;
options.computeFunctionSideEffects = true;

// Remove unused vars also removes unused functions.
options.setRemoveUnusedVariables(Reach.ALL);

// Move code around based on the defined modules.
options.crossModuleCodeMotion = true;
options.crossModuleMethodMotion = true;

// Call optimizations
options.devirtualizePrototypeMethods = true;
options.optimizeParameters = true;
options.optimizeReturns = true;
options.optimizeCalls = true;

从技术上讲，SIMPLE_OPTIMIZATIONS 会给你参数重命名，以防高级启动导致你的代码出现问题（再次来自源代码）：

/**
 * SIMPLE_OPTIMIZATIONS performs transformations to the input JS that do not
 * require any changes to JS that depend on the input JS. For example,
 * function arguments are renamed (which should not matter to code that
 * depends on the input JS), but functions themselves are not renamed (which
 * would otherwise require external code to change to use the renamed function
 * names).
 */