JavaScript, from JSON.parse(), and Firefox
After a comma the parser expects another "key": value pair. When it finds a closing } instead, it reports that it was expecting a property name, which is the parser's way of saying there's a trailing comma.
Both trailing commas are underlined. Press Repair to remove them.
a {
"name": "my-app",
"version": "1.4.0",
"scripts": {
"dev": "next dev",
"build": "next build",
},
"private": true,
}
JavaScript, TypeScript and most config formats allow a comma after the last item, so it slips into JSON files all the time, especially package.json, tsconfig.json and VS Code settings copied around. JSON does not allow it. Delete the comma before the closing brace, or press Repair above.
The same thing in an array gives a slightly different message in Chrome and Node, Unexpected token ']', "[1,2,]" is not valid JSON. The fix is the same, remove the comma before the ].
Code that adds a comma after every item in a loop leaves one dangling at the end. Build the data as an object or array and let JSON.stringify write the commas.
// leaves a trailing comma
let json = '{'
for (const [key, value] of entries) json += `"${key}": "${value}",`
json += '}'
// always valid
const json = JSON.stringify(Object.fromEntries(entries))No. The JSON standard (RFC 8259) has no trailing commas anywhere. JSON5 and JSONC, the format VS Code uses for its settings, do allow them, but JSON.parse and every strict parser will reject them.
Paste the file into the editor above. The error is underlined on the exact line, and the position in the error message counts characters from the start of the file, starting at 0.