Error map

ERR_HTTP_HEADERS_SENT Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client

Node.js · layer 4, Application & API

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Centre: this error. First ring: errors it is linked with (7). Outer ring: what those are linked with. Colours show the layer of a request each error belongs to. Click any dot to re-centre the map on it; hover to follow its connections. The centre dot opens the error page.

1 · On your device 2 · Network 4 · Application & API 5 · Data 7 · Build & delivery
ERR_HTTP_HEADERS_SENT — Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client (Node.js)ERR_HTTP_HE…MODULE_NOT_FOUND — Error: Cannot find module 'x' (MODULE_NOT_FOUND) (Node.js)MODULE_NOT_FOUNDSyntaxError import — SyntaxError: Cannot use import statement outside a module (Node.js)SyntaxError importHeaders already sent — Warning: Cannot modify header information - headers already sent (PHP)Headers already sentDEP0005 — DeprecationWarning: Buffer() is deprecated due to security and usability issues (DEP0005) (Node.js)DEP0005path-to-regexp — TypeError: Missing parameter name at 1 (path-to-regexp) (Node.js)path-to-regexpreq.body undefined — Express: req.body is undefined / {} (body parser missing) (Node.js)req.body undefinedRouter.use middleware — TypeError: Router.use() requires a middleware function but got a Object (Node.js)Router.use middlewa…ERESOLVE — npm ERR! code ERESOLVE — unable to resolve dependency tree (npm)ERESOLVEENOENT — Error: ENOENT: no such file or directory (Node.js)ENOENTTypeError: not a function — TypeError: x is not a function (JavaScript)TypeError: not a fu…ReferenceError — ReferenceError: x is not defined (JavaScript)ReferenceErrorERR_REQUIRE_ESM — Error [ERR_REQUIRE_ESM]: require() of ES Module not supported (Node.js)ERR_REQUIRE_ESMERR_UNKNOWN_FILE_EXTENSION — TypeError [ERR_UNKNOWN_FILE_EXTENSION]: Unknown file extension ".ts" (Node.js)ERR_UNKNOWN_FILE_EX…500 — HTTP 500 Internal Server Error (HTTP)500Call to undefined function — PHP Fatal error: Uncaught Error: Call to undefined function (PHP)Call to undefined f…Undefined array key — Warning: Undefined array key / Undefined index (PHP)Undefined array keyERR_IMPORT_ATTRIBUTE_MISSING — TypeError [ERR_IMPORT_ATTRIBUTE_MISSING]: Module needs an import attribute of "type: json" (Node.js)ERR_IMPORT_ATTRIBUT…Unhandled 'error' event — Error: Unhandled 'error' event (events.js / node:events) (Node.js)Unhandled 'error' e…EBADENGINE — npm WARN EBADENGINE Unsupported engine / The engine "node" is incompatible with this module (Node.js)EBADENGINE404 — HTTP 404 Not Found (HTTP)404405 — HTTP 405 Method Not Allowed (HTTP)405Whitelabel Error Page — Whitelabel Error Page — This application has no explicit mapping for /error (Java)Whitelabel Error Pa…DEP0040 — DeprecationWarning: The `punycode` module is deprecated (DEP0040) (Node.js)DEP0040Mongoose ValidationError — ValidationError: User validation failed: email: Path `email` is required. (Node.js)Mongoose Validation…not a constructor — TypeError: x is not a constructor (JavaScript)not a constructorTDZ — ReferenceError: Cannot access 'x' before initialization (JavaScript)TDZ1046 — MySQL ERROR 1046 (3D000): No database selected (MySQL)1046

Directly related (7)

MODULE_NOT_FOUNDNode.js

Error: Cannot find module 'x' (MODULE_NOT_FOUND)

Node can’t resolve the module path — the package isn’t installed, or a relative path/extension is wrong.

SyntaxError importNode.js

SyntaxError: Cannot use import statement outside a module

An `import` statement ran in a context treated as CommonJS (Node without "type": "module", a browser script without type="module"…

Headers already sentPHP

Warning: Cannot modify header information - headers already sent

You called `header()`, `setcookie()` or `session_start()` after output had already been sent to the browser.

DEP0005Node.js

DeprecationWarning: Buffer() is deprecated due to security and usability issues (DEP0005)

Code (yours or a dependency) uses the deprecated new Buffer() constructor.

path-to-regexpNode.js

TypeError: Missing parameter name at 1 (path-to-regexp)

An Express 5 (path-to-regexp v8) route uses old wildcard syntax like '*' or '/:id?'.

req.body undefinedNode.js

Express: req.body is undefined / {} (body parser missing)

Express didn’t parse the request body because no body-parsing middleware matched the request’s Content-Type.

Router.use middlewareNode.js

TypeError: Router.use() requires a middleware function but got a Object

app.use()/router.use() received an object instead of a function — usually a router module that wasn’t exported.

Two steps away (20)

ERESOLVEnpm

npm ERR! code ERESOLVE — unable to resolve dependency tree

npm 7+ found conflicting peer dependency requirements and refuses to install a broken tree.

ENOENTNode.js

Error: ENOENT: no such file or directory

A file or directory the program tried to open doesn’t exist at that path.

TypeError: not a functionJavaScript

TypeError: x is not a function

You called something as a function, but its value is not a function (it’s undefined, a string, an object…).

ReferenceErrorJavaScript

ReferenceError: x is not defined

Code refers to a variable or function name that doesn’t exist in the current scope.

ERR_REQUIRE_ESMNode.js

Error [ERR_REQUIRE_ESM]: require() of ES Module not supported

CommonJS code used `require()` on a package that is ES-module-only (node-fetch 3, chalk 5, nanoid 4, got 12…).

ERR_UNKNOWN_FILE_EXTENSIONNode.js

TypeError [ERR_UNKNOWN_FILE_EXTENSION]: Unknown file extension ".ts"

Node tried to run a TypeScript file as ESM without a TypeScript loader.

500HTTP

HTTP 500 Internal Server Error

The server hit an unexpected condition — usually an unhandled exception or misconfiguration in the application.

Call to undefined functionPHP

PHP Fatal error: Uncaught Error: Call to undefined function

PHP can’t find the function you called — usually a missing extension, missing include, or namespace issue.

Undefined array keyPHP

Warning: Undefined array key / Undefined index

Your code reads an array key that doesn’t exist — common with `$_GET`, `$_POST` and decoded JSON.

ERR_IMPORT_ATTRIBUTE_MISSINGNode.js

TypeError [ERR_IMPORT_ATTRIBUTE_MISSING]: Module needs an import attribute of "type: json"

An ES module imported a .json file without the required import attribute.

Unhandled 'error' eventNode.js

Error: Unhandled 'error' event (events.js / node:events)

An EventEmitter (stream, socket, child process, server) emitted 'error' and nothing listened for it, so Node crashed.

EBADENGINENode.js

npm WARN EBADENGINE Unsupported engine / The engine "node" is incompatible with this module

A package requires a different Node.js version than the one you’re running.

404HTTP

HTTP 404 Not Found

The server can’t find anything at the requested URL.

405HTTP

HTTP 405 Method Not Allowed

The URL exists, but it doesn’t accept the HTTP method you used (e.g. POST to a GET-only route).

Whitelabel Error PageJava

Whitelabel Error Page — This application has no explicit mapping for /error

Spring Boot’s default error page — the request hit no controller mapping (404) or a controller threw (500).

DEP0040Node.js

DeprecationWarning: The `punycode` module is deprecated (DEP0040)

A dependency imports Node’s built-in punycode module, deprecated since Node 21.

Mongoose ValidationErrorNode.js

ValidationError: User validation failed: email: Path `email` is required.

A document failed Mongoose schema validation before saving.

not a constructorJavaScript

TypeError: x is not a constructor

new was used with something that isn’t a class/constructor — usually a wrong import.

TDZJavaScript

ReferenceError: Cannot access 'x' before initialization

A let/const/class was used before its declaration line ran (temporal dead zone) — often a circular import.

1046MySQL

MySQL ERROR 1046 (3D000): No database selected

A query referenced tables without a database selected (no USE and no db in the connection).

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