Node custom scripting service math

You can create any number of scripting services and invoke them from the REST API. In this example, we'll create a simple service named 'math' that accepts two numbers as query parameters and returns the result as JSON. Since the script is a service, you can control access to it using roles. The script has whatever access to the API that is allowed by the role of the user calling the script. If allowed, the script can make additional REST API calls or cURL requests.

Create the Service

• Go to the services tab in the admin console and click Create.
• Set the Service Type to Script-->Node.js.
• Set the service name to 'math'.
• Set the service label to 'Math'.
• Set the Content to contain the following code then click Create Service.

// To enable Node.js scripting, set the path to node in your DreamFactory .env file.
// This setting is commented out by default.
//
// DF_NODEJS_PATH=/usr/local/bin/node
//
// Use npm to install any dependencies. This script requires 'lodash.'
// Your scripts can call console.log to dump info to the log file in storage/logs.
 
var params, required, n1, n2, resource, result;
 
var lodash = require("lodash");
 
if (event.request.method !== "GET") {
    throw new Error("Only HTTP GET is allowed on this service.");
}
 
// get query params from request
params = event.request.parameters;
 
// get resource, /math —> "", /math/add —> "add"
resource = event.resource;
if (resource !== "") {
    // check for required params
    required = ["n1","n2"];
    lodash._.each( required, function( element ) {
        if (!params.hasOwnProperty(element) || !params[element]) {
            throw new Error( "Missing '" + element + "' in params\n" );
        }
    });
    n1 = Number(params.n1);
    n2 = Number(params.n2);
}
 
switch (resource) {
    case "":
        // /math means return all supported resources
        result = {"resource": ["add", "subtract", "multiply", "divide"]};
        break;
    case "add":
        result = {"result": n1 + n2};
        break;
    case "subtract":
        result = {"result": n1 - n2};
        break;
    case "multiply":
        result = {"result": n1 * n2};
        break;
    case "divide":
        if (!n2) {
            throw new Error("Divide by zero error.");
        }
        result = {"result": n1 / n2};
        break;
    default:
        throw new Error("Invalid or missing resource name.");
        break;
}
 
return result;

Call the service

From any REST client, make the request GET /api/v2/math/subtract?n1=12&n2=8 and you should get back the result of 4. The result is a JSON payload. If you do GET /api/v2/math it returns the list of available operations as an array. A simple REST client can be found at <your_instance_url>/test_rest.html. Remember if you are not an admin user your user role must allow access to the scripting service.