; ids renamed in the template but not in the entry file; SSR shells that do not emit the mount point.","solutions":["Move the script to the end of or add defer/type=\"module\" so the DOM exists first","Confirm the id matches exactly (case-sensitive) in the served HTML and the entry file","Null-check the container and fail fast with a clear message naming the missing selector","If mounting must happen before parse, wrap in DOMContentLoaded"],"exampleFix":"// before (in , element not parsed yet)\nconst root = createRoot(document.getElementById('root'));\n\n// after (deferred entry)\nconst el = document.getElementById('root');\nif (!el) throw new Error('#root not found — check the HTML template');\nconst root = createRoot(el);","handlingStrategy":"type-guard","validationCode":"function isValidReactContainer(node: unknown): boolean {\n return !!(\n node &&\n typeof node === 'object' &&\n (node.nodeType === 1 || node.nodeType === 9 || node.nodeType === 11)\n );\n}\n\nconst el = document.getElementById('root');\nif (!isValidReactContainer(el)) {\n throw new Error('#root not found in the document — check the HTML template and script loading order');\n}\nconst root = createRoot(el);","typeGuard":"function isValidReactContainer(node: unknown): node is Element | Document | DocumentFragment {\n return !!(\n node &&\n typeof node === 'object' &&\n (node.nodeType === 1 || node.nodeType === 9 || node.nodeType === 11)\n );\n}","tryCatchPattern":null,"preventionTips":["Load the entry script with defer, type=\"module\", or at the end of ","Assert the mount element exists on boot with a descriptive error naming the selector","Keep mount-point ids in one shared constant used by both template and entry code"],"tags":["react-dom","createroot","bootstrap","dom","null-container"],"backgroundTag":"invalid-dom-container","analyzedSha":"eafeac097ba51e1eab809c07102126bd5f8e5425","analyzedAt":"2026-08-21T22:01:08.818Z","schemaVersion":2},"datasetVersion":"2026-08-22T04:17:13.399Z"}