Cache regex creation

This is preventive measure to avoid unnecessary regex creation, although the impact is questionable since the fallback pragma is created once at most before the dependencies are collected. So we probably get a single cache hit if we are lucky

packages/core/parcel-bundler/src/transforms/babel/jsx.js

@@ -24,9 +24,17 @@ function createJSXRegexFor(dependency) {
  * package.json is empty or missing yet and therefore pragma cannot
  * be determined based on pkg.dependencies / pkg.devDependencies
  */
+const cacheJsxRegexFor = {};
 function maybeCreateFallbackPragma(asset) {
   for (const dep in JSX_PRAGMA) {
-    if (asset.contents.match(createJSXRegexFor(dep))) {
+    let regex = cacheJsxRegexFor[dep];
+
+    if (!regex) {
+      regex = createJSXRegexFor(dep);
+      cacheJsxRegexFor[dep] = regex;
+    }
+
+    if (asset.contents.match(regex)) {
       return JSX_PRAGMA[dep];
     }
   }