将JS对象转换为字符串，为键/值保留冒号

const obj = {
  name: "John",
  age: 30,
  city: "New York"
};

const jsonString = JSON.stringify(obj);
console.log(jsonString); // 输出: {"name":"John","age":30,"city":"New York"}

function stringifyWithFunctionsAndCircularRefs(obj) {
  const seen = new WeakSet();

  return JSON.stringify(obj, (key, value) => {
    if (typeof value === 'function') {
      return `__FUNCTION__${value.toString()}`;
    }
    if (typeof value === 'object' && value !== null) {
      if (seen.has(value)) {
        return '[Circular]';
      }
      seen.add(value);
    }
    return value;
  });
}

const circularRef = {};
circularRef.self = circularRef;

console.log(stringifyWithFunctionsAndCircularRefs(circularRef)); // 输出: {"self":"[Circular]"}