rosnodejs

https://wiki.ros.org/rosnodejs
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rosnodejs is a pure Node.js implementation of ROS that provides a client library enabling Node.js...
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### Complete Publisher Example

Source: https://wiki.ros.org/rosnodejs/overview/Publishers%20and%20Subscribers

A full example showing node initialization and periodic message publishing.

```javascript
const std_msgs = rosnodejs.require('std_msgs');

rosnodejs.initNode('my_node')
.then((nh) => {
  const pub = nh.advertise('/my_topic', std_msgs.msg.String);
  const msg = new std_msgs.msg.String();
  msg.data = 'Hello, World';
  setInterval(() => {
    pub.publish(msg);
  }, 1000);
});
```

--------------------------------

### Create a Publisher

Source: https://wiki.ros.org/rosnodejs/overview/Publishers%20and%20Subscribers

Demonstrates creating a publisher using a string for the message type or the message class itself.

```javascript
const nh = rosnodejs.nh;
const pub = nh.advertise('/topic', 'std_msgs/String');
```

```javascript
const std_msgs = rosnodejs.require('std_msgs');

const nh = rosnodejs.nh;
const pub = nh.advertise('/topic', std_msgs.msg.String);
```

--------------------------------

### Create and Call a Service Client

Source: https://wiki.ros.org/rosnodejs/overview/services

Initialize a service client via NodeHandle and invoke it by passing a request object. The call returns a promise that resolves with the service response.

```javascript
let serviceClient = nh.serviceClient('/add_two_ints', AddTwoInts);
```

```javascript
let req = new AddTwoInts.Request();
req.a = 1;
req.b = 2;
serviceClient.call(req)
.then((resp) => { console.log(resp); });
```

--------------------------------

### Create a subscriber with a message class

Source: https://wiki.ros.org/rosnodejs/overview/Publishers%20and%20Subscribers

Initializes a subscriber using the message class directly instead of a string.

```javascript
const std_msgs = rosnodejs.require('std_msgs');

const nh = rosnodejs.nh;
const sub = nh.subscribe('/topic', std_msgs.msg.String, () => {});
```

--------------------------------

### Initialize a subscriber with options

Source: https://wiki.ros.org/rosnodejs/overview/Publishers%20and%20Subscribers

Configures a subscriber with an optional object to define queue size and throttling behavior.

```javascript
const options = {...};
const sub = nh.subscribe('/topic', std_msgs.msg.String, () => {}, options);
```

--------------------------------

### Configure Publisher Options

Source: https://wiki.ros.org/rosnodejs/overview/Publishers%20and%20Subscribers

Pass an optional configuration object to customize publisher behavior like latching, queue size, and throttling.

```javascript
const options = {...};
nh.advertise('/topic', std_msgs.msg.String, options);
```

--------------------------------

### Create a subscriber with a string message type

Source: https://wiki.ros.org/rosnodejs/overview/Publishers%20and%20Subscribers

Initializes a subscriber using a string to specify the message type.

```javascript
const callback = function(msg) {
  console.log(msg.data);
}

const nh = rosnodejs.nh;
const sub = nh.subscribe('/topic', 'std_msgs/String', callback);
```

--------------------------------

### Initialize Node for Dynamic Messages

Source: https://wiki.ros.org/rosnodejs/overview/messages

Enable on-the-fly message creation by setting the onTheFly option during node initialization.

```javascript
rosnodejs.initNode('my_node',
                   { onTheFly: true });
```

--------------------------------

### Initialize node with promise handling

Source: https://wiki.ros.org/rosnodejs/overview/Initialization%20and%20Shutdown

Initialization patterns using the promise returned by initNode to access the node handle.

```javascript
rosnodejs.initNode('my_node')
.then((nodeHandle) => {
  // do stuff
});
```

```javascript
rosnodejs.initNode('my_node')
.then(() => {
  let nh = rosnodejs.nh;
  // do stuff
});
```

--------------------------------

### Initialize Message Objects

Source: https://wiki.ros.org/rosnodejs/overview/messages

Create message instances and assign values to fields, either directly or via constructor arguments.

```javascript
const msg = new geometry_msgs.msg.PoseStamped();
msg.header.frame_id = 'base';
```

```javascript
const msg = new std_msgs.msg.String({ data: 'Hello' });
```

--------------------------------

### nh.serviceClient

Source: https://wiki.ros.org/rosnodejs/overview/services

Creates a client to call an existing ROS service.

```APIDOC
## nh.serviceClient(serviceName, serviceType)

### Description
Creates a ServiceClient instance to interact with a specific service.

### Method
NodeHandle.serviceClient

### Parameters
- **serviceName** (string) - Required - The name of the service to call.
- **serviceType** (object) - Required - The service definition module.
```

--------------------------------

### Initialize a ROS node

Source: https://wiki.ros.org/rosnodejs/overview/Initialization%20and%20Shutdown

Basic initialization of a ROS node using the specified node name.

```javascript
rosnodejs.initNode('my_node')
```

--------------------------------

### Advertise a Service with NodeHandle

Source: https://wiki.ros.org/rosnodejs/overview/services

Use advertiseService to register a service callback. The callback receives the request and must populate the response object, returning true on success.

```javascript
const AddTwoInts = rosnodejs.require('ros_tutorials/AddTwoInts');

rosnodejs.initNode('/test_node')
.then((nh) => {
  const addTwoInts = (req, resp) => {
    resp.sum = req.a + req.b;
    return true;
  };

  let service = nh.advertiseService('/add_two_ints', AddTwoInts, addTwoInts);
});
```

--------------------------------

### nh.waitForService

Source: https://wiki.ros.org/rosnodejs/overview/services

Waits for a service to become available.

```APIDOC
## nh.waitForService(serviceName, [timeout])

### Description
Blocks or waits until the specified service is available. Returns a promise that resolves with a boolean indicating availability.

### Method
NodeHandle.waitForService

### Parameters
- **serviceName** (string) - Required - The name of the service to wait for.
- **timeout** (number) - Optional - Maximum time to wait in milliseconds.
```

--------------------------------

### nh.getParam(paramName)

Source: https://wiki.ros.org/rosnodejs/overview/params

Fetches a value from the parameter server. Returns a Promise that resolves with the parameter value.

```APIDOC
## nh.getParam(paramName)

### Description
Fetches a value from the parameter server. The returned Promise resolves with the value of the parameter if it exists.

### Parameters
- **paramName** (string) - Required - The name of the parameter to retrieve.
```

--------------------------------

### nh.advertiseService

Source: https://wiki.ros.org/rosnodejs/overview/services

Advertises a service through the NodeHandle to allow other nodes to call it.

```APIDOC
## nh.advertiseService(serviceName, serviceType, callback)

### Description
Advertises a service so that it can be called by other nodes. The callback function receives the request and response objects.

### Method
NodeHandle.advertiseService

### Parameters
- **serviceName** (string) - Required - The name of the service to advertise.
- **serviceType** (object) - Required - The service definition module.
- **callback** (function) - Required - A function with signature (req, resp) that returns true on success.
```

--------------------------------

### Load Pre-generated Messages

Source: https://wiki.ros.org/rosnodejs/overview/messages

Generate message code for pre-Kinetic ROS environments.

```javascript
rosnodejs.loadAllPackages();
```

--------------------------------

### Check parameter existence

Source: https://wiki.ros.org/rosnodejs/overview/params

Verifies if a parameter exists on the server, returning a Promise that resolves with a boolean.

```javascript
nh.hasParam(paramName)
.then((exists) => {
  console.log('Has param ? ' + exists);
});
```

--------------------------------

### nh.setParam(paramName, paramValue)

Source: https://wiki.ros.org/rosnodejs/overview/params

Sets a value on the parameter server. Supports strings, numbers, booleans, lists, and objects.

```APIDOC
## nh.setParam(paramName, paramValue)

### Description
Sets a value on the parameter server.

### Parameters
- **paramName** (string) - Required - The name of the parameter to set.
- **paramValue** (any) - Required - The value to assign to the parameter.
```

--------------------------------

### Wait for Service Availability

Source: https://wiki.ros.org/rosnodejs/overview/services

Use waitForService to block until a service is available. An optional timeout in milliseconds can be provided, with the promise resolving to a boolean indicating availability.

```javascript
nh.waitForService('/add_two_ints')
.then(() => {
  // call it, presumably
});
```

```javascript
nh.waitForService('/add_two_ints', 1000)
.then((available) => {
  if (available) {
    // as you were
  }
});
```

--------------------------------

### Set parameter values

Source: https://wiki.ros.org/rosnodejs/overview/params

Sets a value on the parameter server. Supports various data types including strings, numbers, lists, and objects.

```javascript
nh.setParam(paramName, paramValue);
```

```javascript
nh.setParam('a_string', 'baz');
nh.setParam('~private_int', 2);
nh.setParam('list_of_floats', [1.1, 2.2, 3.3, 4.4]);
nh.setParam('gains', {'p': 1, 'i': 2, 'd': 3});
```

--------------------------------

### Fetch a parameter value

Source: https://wiki.ros.org/rosnodejs/overview/params

Retrieves a value from the parameter server, returning a Promise that resolves with the parameter value.

```javascript
nh.getParam(paramName)
.then((paramValue) => {
  // a whole new parameter-y world
});
```

--------------------------------

### nh.hasParam(paramName)

Source: https://wiki.ros.org/rosnodejs/overview/params

Checks if the parameter server contains the specified parameter.

```APIDOC
## nh.hasParam(paramName)

### Description
Check if the parameter server has the specified parameter. Returns a Promise that resolves with a boolean indicating existence.

### Parameters
- **paramName** (string) - Required - The name of the parameter to check.
```

--------------------------------

### Publish Messages

Source: https://wiki.ros.org/rosnodejs/overview/Publishers%20and%20Subscribers

Publish messages using an instance of the message object, a generic object, or with a throttle override.

```javascript
const pub = nh.advertise('/my_topic', 'std_msgs/String');
...
const msg = new std_msgs.msg.String();
msg.data = 'Hello!';
pub.publish(msg)
```

```javascript
pub.publish({ data: 'Hello!' });
```

```javascript
pub.publish(msg, -1);
```

--------------------------------

### Require Generated Messages

Source: https://wiki.ros.org/rosnodejs/overview/messages

Load standard message or service types from catkin-generated packages.

```javascript
const std_msgs = rosnodejs.require('std_msgs');
const StringMsg = std_msgs.msg.String;
```

```javascript
const SetBool = rosnodejs.require('std_srvs').srv.SetBool;
```

--------------------------------

### serviceClient.call

Source: https://wiki.ros.org/rosnodejs/overview/services

Invokes the service call with a request object.

```APIDOC
## serviceClient.call(request)

### Description
Calls the service and returns a promise that resolves with the response.

### Method
ServiceClient.call

### Parameters
- **request** (object) - Required - The request message instance.
```

--------------------------------

### Register and remove shutdown hooks

Source: https://wiki.ros.org/rosnodejs/overview/Initialization%20and%20Shutdown

Managing shutdown event listeners for the ROS node. The function passed to removeListener must match the registered listener.

```javascript
rosnodejs.on('shutdown', function() {  });
rosnodejs.once('shutdown', function() {  });
rosnodejs.removeListener('shutdown', function() { });
```

--------------------------------

### nh.deleteParam(paramName)

Source: https://wiki.ros.org/rosnodejs/overview/params

Removes a parameter from the parameter server.

```APIDOC
## nh.deleteParam(paramName)

### Description
Removes a parameter from the parameter server.

### Parameters
- **paramName** (string) - Required - The name of the parameter to delete.
```

--------------------------------

### Delete a parameter

Source: https://wiki.ros.org/rosnodejs/overview/params

Removes a specified parameter from the parameter server.

```javascript
nh.deleteParam(paramName);
```
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