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js-object-to-json

A JavaScript object to JSON converter takes a JavaScript object literal — the kind you'd type into a .js file with unquoted keys, single quotes, or trailing commas — and outputs strict JSON that parsers will accept by adding double quotes around keys, replacing single quotes with double quotes, removing trailing commas, and rejecting JS-only constructs like comments, undefined, functions, or NaN. The ZTools JS Object to JSON Converter handles arbitrarily nested objects, preserves number precision, supports template-literal-style multi-line strings (when valid as JSON strings), reports any JS-specific values that can't convert, and produces both compact and pretty-printed output.

Use cases​

Pasting a JS object literal into a JSON config file​

You copied a const config = \{ ... \} from a JavaScript file. Convert it to valid JSON for a .json config — no manual quoting required.

Sharing JS data with non-JS tools​

Developer says "here's the data" and pastes a JS object. Convert to JSON to feed into Postman, jq, or any non-JS tool.

Building JSON test fixtures from JS examples​

Your test code uses inline objects for setup. To save them as separate .json fixtures, convert and dump to file.

Cleaning up "JSON" you pasted that isn't actually JSON​

A teammate sends you a config they wrote, calling it JSON. It has trailing commas and unquoted keys (i.e., JS). Convert and validate.

How it works​

  1. Paste the JS object literal — Wrap in \{ ... \} or [ ... ]. Trailing commas, unquoted keys, single quotes, comments — all common JS-isms accepted.
  2. Parser tokenizes the JS — A small JS parser interprets the literal. Reports specific JS constructs that can't convert: undefined values, functions, NaN, Infinity, BigInt literals.
  3. Conversion to strict JSON — Keys quoted, single quotes → double quotes, trailing commas removed, comments stripped. Output validated against JSON.parse() before display.
  4. Read both compact and pretty — Two outputs: minified single-line JSON for storage, pretty-printed (2-space indent) for human reading.

Examples​

Input: {name: 'Alice', age: 30,}

Output: {"name":"Alice","age":30}

Input: {users:[{id:1, role:'admin'},{id:2, role:'user'}]}

Output: {"users":[{"id":1,"role":"admin"},{"id":2,"role":"user"}]}

Input: {date: new Date(), fn: () => {}}

Output: ERROR: cannot convert "new Date()" or function values — they have no JSON representation. Convert dates to ISO strings, replace functions with serializable data.

Frequently asked questions​

Why isn't my JavaScript object valid JSON?

Common reasons: 1) keys aren't quoted (name: instead of "name":). 2) Single quotes around strings ('Alice' instead of "Alice"). 3) Trailing commas (\{a:1,\}). 4) Comments. 5) JS-only values (undefined, NaN, functions). The converter handles 1-4 automatically; 5 needs manual replacement.

How does it handle dates?

JavaScript Date objects can't be serialized as JSON directly — they need to become ISO strings. The converter rejects new Date(...) and prompts you to replace with a literal string ISO date like "2026-05-05T00:00:00Z".

What if my object has methods or functions?

JSON has no function representation. The converter rejects function values; you need to remove them or replace with a placeholder string before converting.

Does it handle nested objects?

Yes — any depth. Each level is converted recursively, so nested JS object literals all become valid JSON.

How does it handle BigInt?

BigInt literals (123n) are not valid JSON — JSON only has Number. The converter flags BigInts; convert them to strings before serialization, or accept precision loss.

Tips​

  • For dates, use ISO strings like "2026-05-05T12:34:56Z" — universally parseable, JSON-friendly.
  • For BigInts (very large IDs), convert to strings before JSON serialization to preserve precision.
  • When pasting JS code, include the wrapping braces — paste \{...\}, not name: 'Alice' alone.
  • Always validate the output JSON in a separate parser to confirm round-trip safety.

Try it now​

The full js-object-to-json runs in your browser at https://ztools.zaions.com/js-object-to-json — no signup, no upload, no data leaves your device.

Open the tool ↗

Last updated: 2026-05-05 · Author: Ahsan Mahmood · Edit this page on GitHub