引言
webpack@5.69.0
之前使用taro@3.5.5创建一个taro-react项目之后build了一个weapp项目

最后一步就是启用webpack把react代码编译成weapp

webpack入口
在package.json中可以找到入口文件
这个文件的作用就是引入webpack核心函数（lib/webpack.js）以及工具文件，蓝狮注册抛出整理好之后的webpack核心函数

“main”: “lib/index.js”,
最终输出：

// lib/index.js
// mergeExports是处理fn的，最后输出的就是结果处理的fn
module.exports = mergeExports(fn, {
// 很多webpack内置插件
get webpack() {
return require(“./webpack”); // 核心文件
},
……
})
mergeExports

// lib/index.js
// 第一个参数是对象（函数继承于Fuction，Fuction继承于Object）
const mergeExports = (obj, exports) => {
// 克隆exports对象，传入这个对象里有很多的文件的引入
const descriptors = Object.getOwnPropertyDescriptors(exports);
// 遍历这个对象
for (const name of Object.keys(descriptors)) {
const descriptor = descriptors[name];
if (descriptor.get) {
const fn = descriptor.get;
// 遍历出的属性一个个添加getter到传入的webpack函数
Object.defineProperty(obj, name, {
configurable: false,
enumerable: true,
/**
* memoize就是执行了传入的fn返回一蓝狮注册开户个返回执行之后的结果的一个函数
* memoize(fn)等于
* function(){
* return fn();
* }
/ get: memoize(fn) }); } else if (typeof descriptor.value === “object”) { Object.defineProperty(obj, name, { configurable: false, enumerable: true, writable: false, value: mergeExports({}, descriptor.value) // 递归 }); } else { throw new Error( “Exposed values must be either a getter or an nested object” ); } } // 返回了一个冻结之后的对象，这个对象是个函数，函数里面有很多添加进去的属性方法 return /* @type {A & B} */ (Object.freeze(obj));
};
打印descriptor可以得到如下

{
get: [Function: get webpack],
set: undefined,
enumerable: true,
configurable: true
}
…
{
value: {
ModuleDependency: [Getter],
ConstDependency: [Getter],
NullDependency: [Getter]
},
writable: true,
enumerable: true,
configurable: true
}
…
打印最终返回的

[Function: f] {
webpack: [Getter],
validate: [Getter],
validateSchema: [Getter],
version: [Getter],
cli: [Getter],
AutomaticPrefetchPlugin: [Getter],
AsyncDependenciesBlock: [Getter],
BannerPlugin: [Getter],
Cache: [Getter],
Chunk: [Getter],
ChunkGraph: [Getter],
CleanPlugin: [Getter],
Compilation: [Getter],
Compiler: [Getter],
ConcatenationScope: [Getter],
ContextExclusionPlugin: [Getter],
ContextReplacementPlugin: [Getter],
DefinePlugin: [Getter],
DelegatedPlugin: [Getter],
Dependency: [Getter],
DllPlugin: [Getter],
DllReferencePlugin: [Getter],
DynamicEntryPlugin: [Getter],
EntryOptionPlugin: [Getter],
EntryPlugin: [Getter],
EnvironmentPlugin: [Getter],
EvalDevToolModulePlugin: [Getter],
EvalSourceMapDevToolPlugin: [Getter],
ExternalModule: [Getter],
ExternalsPlugin: [Getter],
Generator: [Getter],
HotUpdateChunk: [Getter],
HotModuleReplacementPlugin: [Getter],
IgnorePlugin: [Getter],
JavascriptModulesPlugin: [Getter],
LibManifestPlugin: [Getter],
LibraryTemplatePlugin: [Getter],
LoaderOptionsPlugin: [Getter],
LoaderTargetPlugin: [Getter],
Module: [Getter],
ModuleFilenameHelpers: [Getter],
ModuleGraph: [Getter],
ModuleGraphConnection: [Getter],
NoEmitOnErrorsPlugin: [Getter],
NormalModule: [Getter],
NormalModuleReplacementPlugin: [Getter],
MultiCompiler: [Getter],
Parser: [Getter],
PrefetchPlugin: [Getter],
ProgressPlugin: [Getter],
ProvidePlugin: [Getter],
RuntimeGlobals: [Getter],
RuntimeModule: [Getter],
SingleEntryPlugin: [Getter],
SourceMapDevToolPlugin: [Getter],
Stats: [Getter],
Template: [Getter],
UsageState: [Getter],
WatchIgnorePlugin: [Getter],
WebpackError: [Getter],
WebpackOptionsApply: [Getter],
WebpackOptionsDefaulter: [Getter],
WebpackOptionsValidationError: [Getter],
ValidationError: [Getter],
cache: { MemoryCachePlugin: [Getter] },
config: {
getNormalizedWebpackOptions: [Getter],
applyWebpackOptionsDefaults: [Getter]
},
dependencies: {
ModuleDependency: [Getter],
ConstDependency: [Getter],
NullDependency: [Getter]
},
ids: {
ChunkModuleIdRangePlugin: [Getter],
NaturalModuleIdsPlugin: [Getter],
OccurrenceModuleIdsPlugin: [Getter],
NamedModuleIdsPlugin: [Getter],
DeterministicChunkIdsPlugin: [Getter],
DeterministicModuleIdsPlugin: [Getter],
NamedChunkIdsPlugin: [Getter],
OccurrenceChunkIdsPlugin: [Getter],
HashedModuleIdsPlugin: [Getter]
},
javascript: {
EnableChunkLoadingPlugin: [Getter],
JavascriptModulesPlugin: [Getter],
JavascriptParser: [Getter]
},
optimize: {
AggressiveMergingPlugin: [Getter],
AggressiveSplittingPlugin: [Getter],
InnerGraph: [Getter],
LimitChunkCountPlugin: [Getter],
MinChunkSizePlugin: [Getter],
ModuleConcatenationPlugin: [Getter],
RealContentHashPlugin: [Getter],
RuntimeChunkPlugin: [Getter],
SideEffectsFlagPlugin: [Getter],
SplitChunksPlugin: [Getter]
},
runtime: {
GetChunkFilenameRuntimeModule: [Getter],
LoadScriptRuntimeModule: [Getter]
},
prefetch: { ChunkPrefetchPreloadPlugin: [Getter] },
web: {
FetchCompileAsyncWasmPlugin: [Getter],
FetchCompileWasmPlugin: [Getter],
JsonpChunkLoadingRuntimeModule: [Getter],
JsonpTemplatePlugin: [Getter]
},
webworker: { WebWorkerTemplatePlugin: [Getter] },
node: {
NodeEnvironmentPlugin: [Getter],
NodeSourcePlugin: [Getter],
NodeTargetPlugin: [Getter],
NodeTemplatePlugin: [Getter],
ReadFileCompileWasmPlugin: [Getter]
},
electron: { ElectronTargetPlugin: [Getter] },
wasm: { AsyncWebAssemblyModulesPlugin: [Getter] },
library: { AbstractLibraryPlugin: [Getter], EnableLibraryPlugin: [Getter] },
container: {
ContainerPlugin: [Getter],
ContainerReferencePlugin: [Getter],
ModuleFederationPlugin: [Getter],
scope: [Getter]
},
sharing: {
ConsumeSharedPlugin: [Getter],
ProvideSharedPlugin: [Getter],
SharePlugin: [Getter],
scope: [Getter]
},
debug: { ProfilingPlugin: [Getter] },
util: {
createHash: [Getter],
comparators: [Getter],
runtime: [Getter],
serialization: [Getter],
cleverMerge: [Getter],
LazySet: [Getter]
},
sources: [Getter],
experiments: {
schemes: { HttpUriPlugin: [Getter] },
ids: { SyncModuleIdsPlugin: [Getter] }
}
}