Error map
unexpected end of input SyntaxError: Unexpected end of input
JavaScript · layer 1, On your device
Centre: this error. First ring: errors it is linked with (12). 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.
Directly related (12)
com.fasterxml.jackson.databind.exc.InvalidDefinitionException: No serializer found for class X and no properties discovered
Jackson can’t serialize the class — it has no public getters/fields, or it’s a Hibernate proxy, or Java 8 date types without the…
com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize value of type `java.util.ArrayList` from Object value
Jackson found JSON whose shape doesn’t match the target Java type (object vs array, string vs number, missing constructor).
API Error: Malformed JSON in request body (entity.parse.failed / JSON parse error)
The server couldn’t parse the request body as JSON, so it rejected the request before looking at any field.
Dockerfile parse error line N: unknown instruction
A line in the Dockerfile doesn’t start with a valid instruction — usually a broken line continuation or a typo.
System.Text.Json: '<' is an invalid start of a value. Path: $ | LineNumber: 0 | BytePositionInLine: 0
The response wasn’t JSON — usually an HTML error page, login redirect, or an empty body was passed to the JSON deserializer.
SyntaxError: Invalid regular expression: /x/: Unterminated group
A regex pattern has invalid syntax — unbalanced parentheses/brackets or unescaped special characters.
json_decode() returns null / JSON_ERROR_SYNTAX: Syntax error
The string passed to json_decode isn’t valid JSON, so PHP returns null.
SyntaxError: Unexpected token < in JSON at position 0
`JSON.parse()` / `response.json()` received something that isn’t JSON — very often an HTML error page.
TypeError: Converting circular structure to JSON
JSON.stringify met an object that references itself (directly or through children).
SyntaxError: Identifier 'x' has already been declared
The same let/const/class name was declared twice in the same scope.
SyntaxError: await is only valid in async functions and the top level bodies of modules
await was used inside a function that isn’t async (or in a classic, non-module script).
SyntaxError: Unexpected identifier
The parser found a name where it expected punctuation — usually a missing comma, operator or quote.
Two steps away (30)
JsonException: A possible object cycle was detected
System.Text.Json found a reference loop (e.g. Order → Customer → Orders → …) while serialising, usually from EF Core navigation p…
com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "x", not marked as ignorable
The JSON contains a field your Java class doesn’t have, and Jackson is configured to fail on unknown properties.
org.hibernate.LazyInitializationException: could not initialize proxy - no Session
A lazy-loaded association was accessed after the Hibernate session/transaction closed.
HttpMessageNotReadableException: JSON parse error / Required request body is missing
Spring couldn’t read the request body into your @RequestBody object.
npm ERR! code EJSONPARSE — Failed to parse json / Unexpected token in JSON at position
package.json (or package-lock.json) contains invalid JSON.
json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)
The text passed to json.loads() isn’t JSON — at char 0 it’s usually empty or HTML.
HTTP 400 Bad Request
The server could not understand the request because its syntax, headers or body are malformed or invalid.
HTTP 415 Unsupported Media Type
The server refuses the request because the body’s Content-Type isn’t one it accepts.
HTTP 411 Length Required
The server refuses a request with a body but no Content-Length header.
PHP Parse error: syntax error, unexpected …
PHP can’t parse the file because of a syntax mistake — the real error is often on the line before the one reported.
IndentationError: unexpected indent / expected an indented block
Python’s block structure is broken — inconsistent indentation or mixed tabs and spaces.
npm ERR! code ELIFECYCLE / Command failed with exit code 1
An npm script (build, start, test, postinstall) exited with an error. ELIFECYCLE is only the wrapper — the real error is printed…
TypeError: Object of type datetime is not JSON serializable
json.dumps() met a type it doesn’t know how to encode (datetime, Decimal, set, custom objects).
HttpRequestException: The SSL connection could not be established, see inner exception. (AuthenticationException: The remote certificate is invalid)
HttpClient couldn’t complete the TLS handshake — untrusted/self-signed certificate, name mismatch, expired certificate, or TLS ve…
HttpRequestException: No connection could be made because the target machine actively refused it (localhost:5001)
Nothing is listening on the host/port the client called — the API isn’t running, uses another port, or the container/network addr…
SyntaxError: Unexpected token '<' (HTML served instead of JavaScript)
The browser loaded a .js file but received HTML (an error page or the SPA index.html).
SyntaxError: missing ) after argument list
A function call’s parentheses are unbalanced — often an unescaped quote or a missing comma/plus.
SyntaxError: Invalid or unexpected token
The code contains a character the parser can’t handle — smart quotes, stray characters or an unterminated string.
System.Text.Json.JsonException: The JSON value could not be converted to System.Int32. Path: $.id
System.Text.Json couldn’t map a JSON value to the target .NET type — e.g. "42" (string) to int, null to a non-nullable type, or w…
Newtonsoft.Json.JsonReaderException: Unexpected character encountered while parsing value: <. Path '', line 0, position 0
Json.NET was given text that isn’t valid JSON — commonly HTML, a BOM, or an already-serialized string.
HTTP 404 Not Found
The server can’t find anything at the requested URL.
HTTP 500 Internal Server Error
The server hit an unexpected condition — usually an unhandled exception or misconfiguration in the application.
TypeError: Failed to fetch / NetworkError when attempting to fetch resource
The browser couldn’t complete the request at the network level — CORS, DNS, offline, blocked mixed content, or the server refused…
ReferenceError: x is not defined
Code refers to a variable or function name that doesn’t exist in the current scope.
NameError: name 'x' is not defined
Python doesn’t know the name — it was never assigned/imported in this scope, or it’s misspelled.
ReferenceError: Cannot access 'x' before initialization
A let/const/class was used before its declaration line ran (temporal dead zone) — often a circular import.
Node.js: [UnhandledPromiseRejection] — This error originated either by throwing inside of an async function without a catch block
A promise rejected and nothing handled it; since Node 15 this crashes the process.
AbortError: The user aborted a request. / signal is aborted without reason
A fetch was cancelled through an AbortController (or the browser cancelled it).
TypeError: Failed to execute 'json' on 'Response': body stream already read
A fetch Response body was consumed twice (e.g. calling .text() then .json()).
GraphQL: Syntax Error: Expected Name, found <EOF> / Unexpected }
The GraphQL document is malformed — unbalanced braces, a stray comma/character, or an empty query.
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