Language

RockScript is a subset of JavaScript (ECMAScript 5.1). The main goal of RockScript is to support resilient, non-blocking script execution. We aim to implement the most used constructs to enable the stitching of service functions.

This page documents which subset of JavaScript is supported. We leverage JavaScript for developers to reduce the learning curve and it’s the perfect language to juggle with JSON, which most API’s use these days. But we do not aim to cover the complete language syntax. If you wonder why RockScript doesn’t just use Node.js, see at the bottom of this page.

See the Roadmap for what’s next.

System variable

The system variable is made available to every script. It provides a mechanism to import activities, access the script input and (over time) other interactions with the runtime server environment.

system.import

E.g.

var http = system.import('rockscript.io/http');

system.import(url) returns a script object that exposes activities as functions.

To learn about how to add activities to the engine, see Services

system.input

When starting a script, you can pass in data. That input data is made available in the script under the system.input property.

An example:

POST http://localhost:3652/command 
Content-Type: application/json
{ "startScript" : {
    "scriptId": "s726",
    "input": {
      "orderId": "9sdf8",
      "countryCode": "01" 
    }
}}

You can access the countryCode in the script like this:

var countryCode = system.input.countryCode;

Script block

Just like in JavaScript environments, the full script text itself is considered a block and the list of statements are executed sequential.

Variable declaration

Examples

var variableName;
var variableName = 'initial value';
var variableName = system.import('rockscript.io/http');

Assignment

Examples

result = 'initial value';
result.message = 'hello';
result.message['firstName'] = 'John';

If-then-else

The condition expression will be converted to a boolean. See also Comparison operator expressions for which comparators are supported.

Examples

if (msg=='call') http.get({url: '...'});

var someVar = {thisConverts:'to boolean true'};
if (someVar) http.get({url: '...'});

if (flipper==='on') {
  http.get({url: '...'});
  flipper = 'off';
} else {
  flipper = 'on';
}

Loops

For now, only 1 form of loop is supported.

Example

for (var i=0; i<a.length; i++) {
  total = total + a[i];
}

Limitation: Other forms of loops are not yet supported like do while, while do, for (non-var-declaring-expression;...;...), for (a in b) and for (var a in b)

Default functions and properties

Strings and arrays do not have any predefined functions and properties except for property length.

Example

var a = [1, 2, 3];
for (var i=0; i<a.length; i++) {
  total = total + a[i];
}

Declaring functions

At the moment we don’t support declaration of functions in the script. We’re believe it’s best to leave out functions so that each script remains the scope of 1 function. But this is still a hypothesis that we’re seeking validation on. So your input is greatly appreciated.

Expressions

Literals

Examples

'some text'
1
5.0
true
false
{ country: 'US' }
[ 'a', 'b', 'c']

Variable expressions

Examples

variableName
variableName.propertName;
variableName.propertyName(arg0, arg1);
variableName[propertyName];

Or a combination of the above like eg

variableName.propertyName(arg0, arg1)['field'].anotherPropertyName;

Note that for service function invocations, any number of args is allowed.

Comparison operators

All of Equality comparisons and sameness is implemented

Limitation: While all automatic type conversions are implemented, object conversion functions like toString and valueOf are not invoked yet.

Examples

text=='some text'
'25' != service.getSomeNumber()
text==='some text'
5 < totalAmount
true > 0
customer.getAge() <= 25
'hello' >= company.getName()

Arithmic operators

All the addition conversions are correctly applied like in Node.js

Supported: +, -, *, /, ++, --

Examples

'hello' + ' world' 
5 + ' EUR'
'Formula ' + true
count * 5
i++

Limitations: % and ** are not yet supported.
And for the conversions, while all automatic type conversions are implemented, object conversion functions like toString and valueOf are not invoked yet.

Logical operators and parenthesis

Examples

!(true || false) && true

RockScript vs Node.js

The purpose of RockScript is resilient script execution. In order to do this, we need continuations. This means that need the ability to serialize the complete runtime state of a script execution when the script is waiting for external callbacks. And when the server gets a callback, we need to restore the runtime state from the persisted state and then resume execution at that position in the script. Serializing and deserializing execution state and resuming an execution after deserializing it is something that other script engines can’t do so that’s why we created RockScript.