Start to add code

Author: keller-mark

.gitignore

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+.DS_Store
+node_modules
+dist

rollup.config.js

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+import fs from 'fs';
+import replace from '@rollup/plugin-replace';
+import path from 'path';
+
+const version = JSON.parse(fs.readFileSync('package.json')).version;
+
+export default [
+  config(true, false),
+  config(false, false),
+  config(false, true),
+];
+
+function config (isWasm, isDebug) {
+  const name = 'es-module-shims'
+
+  return {
+    input: `src/${name}.js`,
+    output: {
+      file: `dist/${name}${isWasm ? '.wasm' : ''}${isDebug ? '.debug' : ''}.js`,
+      format: 'iife',
+      strict: false,
+      sourcemap: false,
+      banner: `/* ES Module Shims ${isWasm ? 'Wasm ' : ''}${isDebug ? 'DEBUG BUILD ' : ''}${version} */`
+    },
+    plugins: [
+      {
+        resolveId (id) {
+          if (isWasm && id === '../node_modules/es-module-lexer/dist/lexer.asm.js')
+            return path.resolve('node_modules/es-module-lexer/dist/lexer.js');
+        }
+      },
+      replace({
+        'self.ESMS_DEBUG': isDebug.toString(),
+        preventAssignment: true
+      }),
+    ]
+  };
+}

src/dynamic-import.js

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+import { createBlob, baseUrl, nonce, hasDocument } from './env.js';
+
+export let dynamicImport = !hasDocument && (0, eval)('u=>import(u)');
+
+export let supportsDynamicImport;
+
+export const dynamicImportCheck = hasDocument && new Promise(resolve => {
+  const s = Object.assign(document.createElement('script'), {
+    src: createBlob('self._d=u=>import(u)'),
+    ep: true
+  });
+  s.setAttribute('nonce', nonce);
+  s.addEventListener('load', () => {
+    if (!(supportsDynamicImport = !!(dynamicImport = self._d))) {
+      let err;
+      window.addEventListener('error', _err => err = _err);
+      dynamicImport = (url, opts) => new Promise((resolve, reject) => {
+        const s = Object.assign(document.createElement('script'), {
+          type: 'module',
+          src: createBlob(`import*as m from'${url}';self._esmsi=m`)
+        });
+        err = undefined;
+        s.ep = true;
+        if (nonce)
+          s.setAttribute('nonce', nonce);
+        // Safari is unique in supporting module script error events
+        s.addEventListener('error', cb);
+        s.addEventListener('load', cb);
+        function cb (_err) {
+          document.head.removeChild(s);
+          if (self._esmsi) {
+            resolve(self._esmsi, baseUrl);
+            self._esmsi = undefined;
+          }
+          else {
+            reject(!(_err instanceof Event) && _err || err && err.error || new Error(`Error loading ${opts && opts.errUrl || url} (${s.src}).`));
+            err = undefined;
+          }
+        }
+        document.head.appendChild(s);
+      });
+    }
+    document.head.removeChild(s);
+    delete self._d;
+    resolve();
+  });
+  document.head.appendChild(s);
+});

src/env.js

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+export const hasWindow = typeof window !== 'undefined';
+export const hasDocument = typeof document !== 'undefined';
+
+export const noop = () => {};
+
+const optionsScript = hasDocument ? document.querySelector('script[type=esms-options]') : undefined;
+
+export const esmsInitOptions = optionsScript ? JSON.parse(optionsScript.innerHTML) : {};
+Object.assign(esmsInitOptions, self.esmsInitOptions || {});
+
+export let shimMode = hasDocument ? !!esmsInitOptions.shimMode : true;
+
+export const importHook = globalHook(shimMode && esmsInitOptions.onimport);
+export const resolveHook = globalHook(shimMode && esmsInitOptions.resolve);
+export let fetchHook = esmsInitOptions.fetch ? globalHook(esmsInitOptions.fetch) : fetch;
+export const metaHook = esmsInitOptions.meta ? globalHook(shimMode && esmsInitOptions.meta) : noop;
+
+export const mapOverrides = esmsInitOptions.mapOverrides;
+
+export let nonce = esmsInitOptions.nonce;
+if (!nonce && hasDocument) {
+  const nonceElement = document.querySelector('script[nonce]');
+  if (nonceElement)
+    nonce = nonceElement.nonce || nonceElement.getAttribute('nonce');
+}
+
+export const onerror = globalHook(esmsInitOptions.onerror || noop);
+export const onpolyfill = esmsInitOptions.onpolyfill ? globalHook(esmsInitOptions.onpolyfill) : () => {
+  console.log('%c^^ Module TypeError above is polyfilled and can be ignored ^^', 'font-weight:900;color:#391');
+};
+
+export const { revokeBlobURLs, noLoadEventRetriggers, enforceIntegrity } = esmsInitOptions;
+
+function globalHook (name) {
+  return typeof name === 'string' ? self[name] : name;
+}
+
+const enable = Array.isArray(esmsInitOptions.polyfillEnable) ? esmsInitOptions.polyfillEnable : [];
+export const cssModulesEnabled = enable.includes('css-modules');
+export const jsonModulesEnabled = enable.includes('json-modules');
+
+export const edge = !navigator.userAgentData && !!navigator.userAgent.match(/Edge\/\d+\.\d+/);
+
+export const baseUrl = hasDocument
+  ? document.baseURI
+  : `${location.protocol}//${location.host}${location.pathname.includes('/') 
+    ? location.pathname.slice(0, location.pathname.lastIndexOf('/') + 1) 
+    : location.pathname}`;
+
+export const createBlob = (source, type = 'text/javascript') => URL.createObjectURL(new Blob([source], { type }));
+export let { skip } = esmsInitOptions;
+if (Array.isArray(skip)) {
+  const l = skip.map(s => new URL(s, baseUrl).href);
+  skip = s => l.some(i => i[i.length - 1] === '/' && s.startsWith(i) || s === i);
+}
+else if (typeof skip === 'string') {
+  const r = new RegExp(skip);
+  skip = s => r.test(s);
+}
+
+const eoop = err => setTimeout(() => { throw err });
+
+export const throwError = err => { (self.reportError || hasWindow && window.safari && console.error || eoop)(err), void onerror(err) };
+
+export function fromParent (parent) {
+  return parent ? ` imported from ${parent}` : '';
+}
+
+export let importMapSrcOrLazy = false;
+
+export function setImportMapSrcOrLazy () {
+  importMapSrcOrLazy = true;
+}
+
+// shim mode is determined on initialization, no late shim mode
+if (!shimMode) {
+  if (document.querySelectorAll('script[type=module-shim],script[type=importmap-shim],link[rel=modulepreload-shim]').length) {
+    shimMode = true;
+  }
+  else {
+    let seenScript = false;
+    for (const script of document.querySelectorAll('script[type=module],script[type=importmap]')) {
+      if (!seenScript) {
+        if (script.type === 'module' && !script.ep)
+          seenScript = true;
+      }
+      else if (script.type === 'importmap' && seenScript) {
+        importMapSrcOrLazy = true;
+        break;
+      }
+    }
+  }
+}