在javascript中更改json值的数据类型

var jsonStr = '{"name": "John", "age": 30}';
var jsonObj = JSON.parse(jsonStr);
jsonObj.age = 31;
var modifiedJsonStr = JSON.stringify(jsonObj);

var jsonObj = {"name": "John", "age": 30};
var modifiedObj = Object.assign({}, jsonObj);
modifiedObj.age = 31;
var modifiedJsonStr = JSON.stringify(modifiedObj);

function modifyJsonValue(obj, key, newValue) {
  for (var prop in obj) {
    if (obj.hasOwnProperty(prop)) {
      if (prop === key) {
        obj[prop] = newValue;
      } else if (typeof obj[prop] === 'object') {
        modifyJsonValue(obj[prop], key, newValue);
      }
    }
  }
}

var jsonObj = {"name": "John", "age": 30, "address": {"city": "New York"}};
modifyJsonValue(jsonObj, "age", 31);
var modifiedJsonStr = JSON.stringify(jsonObj);