Complex message type altered after bridge server sending back to clients

For complex message type, like sensor_msgs/msg/JointState, the message object altered when the rosbridge server tried sending back it to the clients. Here it is:

• publish sensor_msg/msg/JointState message type:

{ op: 'publish', id: 'publish_setup_jointstate', topic: 'subscribe_jointstate_topic',
  msg: {
    header: {
      stamp: {
        sec: 123456, nanosec: 789
      },
      frame_id: 'main frame'},
    name: ['Tom', 'Jerry'],
    position: [1, 2],
    velocity: [2, 3],
    effort: [4, 5, 6]}}

• Returned response:

{ op: 'publish', topic: 'subscribe_jointstate_topic',
  msg: {
    header: {
        stamp: [Object],
        frame_id: 'main frame' },
     name: [ 'Tom', 'Jerry' ],
     position: { '0': 1, '1': 2 },
     velocity: { '0': 2, '1': 3 },
     effort: { '0': 4, '1': 5, '2': 6 } } }

The structure of the message altered after serialization. This happened when calling JSON.stringify() and JSON.parse() of the JointState message object.

[qiuzhong]

We should figure out why before a publisher node sending this JointState type message, the JSON.stringify works:

{"header":{
    "stamp":{
      "sec":123456,
      "nanosec":789},
 "frame_id":"main frame"},
 "name":["Tom","Jerry"],
 "position":[1,2],
  "velocity":[2,3],
  "effort":[4,5,6]}

While a subscription node received this message, then the JSON.stringify didn’t work:

{ "header":{
    "stamp":{
    "sec":123456,
    "nanosec":789},
  "frame_id":"main frame"},
  "name":["Tom","Jerry"],
  "position":{"0":1,"1":2},
  "velocity":{"0":2,"1":3},
  "effort":{"0":4,"1":5,"2":6}}

[minggangw]

So let’s close this issue.