Function parseJsonFromDirtyString

parseJsonFromDirtyString(data: string): unknown

Extracts and parses the first top-level JSON array or object from a string that may contain trailing non-JSON content (e.g. delimiters like "&&&").

Parameters

data: string
The string containing JSON with possible trailing junk

Returns unknown

The parsed JSON value

Throws

Error if no JSON array/object is found or if the JSON is malformed

Example

parseJsonFromDirtyString('[ "a", "b" ]\n&&&\n') // Returns ["a", "b"]
parseJsonFromDirtyString('{"key": "val"} some junk') // Returns {key: "val"}

Source

export function parseJsonFromDirtyString(data: string): unknown {
  const trimmed = data.trim();
  const openBracket = trimmed.search(/[\[{]/);
  if (openBracket === -1) throw new Error("No JSON array or object found in string");

  const openChar = trimmed[openBracket];
  const closeChar = openChar === "[" ? "]" : "}";
  let depth = 0;
  let inString = false;
  let escaped = false;

  for (let i = openBracket; i < trimmed.length; i++) {
    const ch = trimmed[i];
    if (escaped) {
      escaped = false;
      continue;
    }
    if (ch === "\\") {
      escaped = true;
      continue;
    }
    if (ch === '"') {
      inString = !inString;
      continue;
    }
    if (inString) continue;
    if (ch === openChar) depth++;
    else if (ch === closeChar) depth--;
    if (depth === 0) {
      return JSON.parse(trimmed.slice(openBracket, i + 1));
    }
  }

  throw new Error("Unterminated JSON in string");
}