How to Fix "Unexpected Token" and Other Invalid JSON Errors
Errors such as "Unexpected token } in JSON at position 42" or "Expected property name or '}'" almost always come from a small syntax slip. JSON is stricter than JavaScript object syntax, and it is easy to write something that looks fine but is not valid. These are the mistakes behind the vast majority of parse errors. 1. Trailing commas JSON does not allow a comma after the last item in an object…
Unexpected token and other invalid JSON errors typically arise due to small syntax mistakes. JSON is stricter than JavaScript object syntax, making it easy to write something that appears correct but is actually invalid. The most common error stems from trailing commas, which JSON does not allow after the last item in an object or array.
For instance, { a : 1 , b : 2 } is invalid, whereas { a : 1 , b : 2 } is correct. Additionally, JSON requires the use of double quotes for strings and keys, as single quotes are not permitted. Another frequent issue is the use of unquoted keys, which JavaScript allows but JSON does not. Comments are also not supported in standard JSON; instead, use JSONC, JSON5, YAML, or strip comments before parsing.
Values such as undefined, NaN, and Infinity are invalid, and numbers should not contain leading zeros or leading plus signs. Invisible issues, like a byte-order mark (BOM) at the beginning of a file or two objects back-to-back without a closing brace or bracket, can also cause unexpected token errors. To resolve these problems, copy the exact text being parsed and paste it into a validator, which should indicate the line and column of the first error. Focus on fixing one error at a time and re-validate to ensure the issue is resolved.
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