docs：更新文档

node_modules/es-module-lexer/README.md

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+# ES Module Lexer
+
+[![Build Status][travis-image]][travis-url]
+
+A JS module syntax lexer used in [es-module-shims](https://github.com/guybedford/es-module-shims).
+
+Outputs the list of exports and locations of import specifiers, including dynamic import and import meta handling.
+
+A very small single JS file (4KiB gzipped) that includes inlined Web Assembly for very fast source analysis of ECMAScript module syntax only.
+
+For an example of the performance, Angular 1 (720KiB) is fully parsed in 5ms, in comparison to the fastest JS parser, Acorn which takes over 100ms.
+
+_Comprehensively handles the JS language grammar while remaining small and fast. - ~10ms per MB of JS cold and ~5ms per MB of JS warm, [see benchmarks](#benchmarks) for more info._
+
+### Usage
+
+```
+npm install es-module-lexer
+```
+
+For use in CommonJS:
+
+```js
+const { init, parse } = require('es-module-lexer');
+
+(async () => {
+  // either await init, or call parse asynchronously
+  // this is necessary for the Web Assembly boot
+  await init;
+
+  const [imports, exports] = parse('export var p = 5');
+  exports[0] === 'p';
+})();
+```
+
+An ES module version is also available from `dist/lexer.js`:  
+Note: This version will be automatically used in rollup/es-dev-server/node (if an es-module project)
+
+```js
+import { init, parse } from 'es-module-lexer/dist/lexer.js';
+
+(async () => {
+  await init;
+
+  const source = `
+    import { a } from 'asdf';
+    export var p = 5;
+    export function q () {
+
+    };
+
+    // Comments provided to demonstrate edge cases
+    import /*comment!*/ ('asdf');
+    import /*comment!*/.meta.asdf;
+  `;
+
+  const [imports, exports] = parse(source, 'optional-sourcename');
+
+  // Returns "asdf"
+  source.substring(imports[0].s, imports[0].e);
+  // "s" is shorthand for "start"
+  // "e" is shorthand for "end"
+
+  // Returns "import { a } from 'asdf';"
+  source.substring(imports[0].ss, imports[0].se);
+  // "ss" is shorthand for "statement start"
+  // "se" is shorthand for "statement end"
+
+  // Returns "p,q"
+  exports.toString();
+
+  // Dynamic imports are indicated by imports[1].d > -1
+  // In this case the "d" index is the start of the dynamic import
+  // Returns true
+  imports[1].d > -1;
+
+  // Returns "'asdf'"
+  source.substring(imports[1].s, imports[1].e);
+  // Returns "import /*comment!*/ ("
+  source.substring(imports[1].d, imports[1].s);
+  // Returns "import /*comment!*/ ('asdf')"
+  source.substring(imports[1].d, imports[1].e + 1);
+  // imports[1].ss and imports[1].se is not meaningful 
+  // because dynamic import is not a statement
+
+  // import.meta is indicated by imports[2].d === -2
+  // Returns true
+  imports[2].d === -2;
+  // Returns "import /*comment!*/.meta"
+  source.substring(imports[2].s, imports[2].e);
+})();
+```
+
+### Facade Detection
+
+Facade modules that only use import / export syntax can be detected via the third return value:
+
+```js
+const [,, facade] = parse(`
+  export * from 'external';
+  import * as ns from 'external2';
+  export { a as b } from 'external3';
+  export { ns };
+`);
+facade === true;
+```
+
+### Environment Support
+
+Node.js 10+, and [all browsers with Web Assembly support](https://caniuse.com/#feat=wasm).
+
+### Grammar Support
+
+* Token state parses all line comments, block comments, strings, template strings, blocks, parens and punctuators.
+* Division operator / regex token ambiguity is handled via backtracking checks against punctuator prefixes, including closing brace or paren backtracking.
+* Always correctly parses valid JS source, but may parse invalid JS source without errors.
+
+### Limitations
+
+The lexing approach is designed to deal with the full language grammar including RegEx / division operator ambiguity through backtracking and paren / brace tracking.
+
+The only limitation to the reduced parser is that the "exports" list may not correctly gather all export identifiers in the following edge cases:
+
+```js
+// Only "a" is detected as an export, "q" isn't
+export var a = 'asdf', q = z;
+
+// "b" is not detected as an export
+export var { a: b } = asdf;
+```
+
+The above cases are handled gracefully in that the lexer will keep going fine, it will just not properly detect the export names above.
+
+### Benchmarks
+
+Benchmarks can be run with `npm run bench`.
+
+Current results:
+
+```
+Module load time
+> 7ms
+Cold Run, All Samples
+test/samples/*.js (3057 KiB)
+> 33ms
+
+Warm Runs (average of 25 runs)
+test/samples/angular.js (719 KiB)
+> 4.08ms
+test/samples/angular.min.js (188 KiB)
+> 2.08ms
+test/samples/d3.js (491 KiB)
+> 4.72ms
+test/samples/d3.min.js (274 KiB)
+> 3ms
+test/samples/magic-string.js (34 KiB)
+> 0.04ms
+test/samples/magic-string.min.js (20 KiB)
+> 0ms
+test/samples/rollup.js (902 KiB)
+> 8.16ms
+test/samples/rollup.min.js (429 KiB)
+> 4.28ms
+
+Warm Runs, All Samples (average of 25 runs)
+test/samples/*.js (3057 KiB)
+> 25.68ms
+```
+
+### Building
+
+To build download the WASI SDK from https://github.com/WebAssembly/wasi-sdk/releases.
+
+The Makefile assumes the existence of "wasi-sdk-11.0" and "wabt" (optional) as sibling folders to this project.
+
+The build through the Makefile is then run via `make lib/lexer.wasm`, which can also be triggered via `npm run build-wasm` to create `dist/lexer.js`.
+
+On Windows it may be preferable to use the Linux subsystem.
+
+After the Web Assembly build, the CJS build can be triggered via `npm run build`.
+
+### License
+
+MIT
+
+[travis-url]: https://travis-ci.org/guybedford/es-module-lexer
+[travis-image]: https://travis-ci.org/guybedford/es-module-lexer.svg?branch=master