Blank JavaScript

The JavaScript operator allows you to execute JavaScript snippets within a graph. This is a blank operator, the input and output ports can be added and also the desired javascript snippet.

Configuration Parameters

Parameter	Type	Description
codelanguage	string	The programming language used in the snippet. Default: "javascript"
script	string	Mandatory. The inline script to be executed. If the script starts with "file://", then the script file is executed. Default: ""

Parameter

Type

Description

codelanguage

string

The programming language used in the snippet.

Default: "javascript"

script

string

Mandatory. The inline script to be executed. If the script starts with "file://", then the script file is executed.

Default: ""

Input

None

Output

None

Creating a JavaScript Extension

Create an extension of the JavaScript operator and add the desired input and output ports.
Add your JavaScript snippet as an inline "script" parameter in the extension configuration or put the code into a separate file and use the prefix "file://" to specify the file name.

Basic Example

Count all incoming messages on the "input" port and write the count to the output port:

var counter = 0

$.setPortCallback("input",onInput)

function onInput(ctx,s) {
    counter++
    $.output(counter)
}

Generators

Generators are functions that are executed before the event processing loop starts.

For example:

var counter = 0

$.addGenerator(gen)
$.addGenerator(gen)

function gen(ctx) {
    for (var i = 0; i < 3; i++ ) {
      $.output(counter)
      counter++
    }
}

This example produces the values 0,1,2,3,4,5 on the output port "output".

Timers

This example produces the values 0,1,2,3,4,5 on the output port "output".

For example:

var counter = 0

$.addTimer("1s",t1)

function t1(ctx) {
  $.output(counter)
  counter++
}

This example produces the values 0,1,2... on port "output" until graph shutdown.

Shutdown Handlers

This example produces the values 0,1,2... on port "output" until graph shutdown.

For example:

var counter = 0

$.setPortCallback("input",onInput)

function onInput(ctx,s) {
    counter++
}

function shutdown(ctx) {
    $.output(counter)
}

$.addShutdownHandler(shutdown)
$.addShutdownHandler(shutdown)

This example produces values 7,7 if 7 values have been provided on the "input" port.

Configuration API

Configuration API provides the ability to read the configuration provided via a graph description.

For example:

function gen(ctx) {
  $.str($.config.getString("str"))
  $.int($.config.getInt("int"))
  $.bool(""+$.config.getBool("bool"))
  $.msg({Attributes: $.config.getObject("obj")})
  $.msg({Attributes: $.config.asObject()})
}
$.addGenerator(gen)

This example reads the configuration of the operator and provides the given values on the output ports.

Error Handling

The fail function provides the ability to terminate a processing loop in case of an internal error.

For example:

var counter = 0

$.setPortCallback("input",onInput)

function onInput(ctx,s) {
    counter++
    if (counter > 1 ) {
      $.fail("Failure in counter")
    }
    $.output(counter)
}

This example terminates the loop while processing the second input on "input" port.