V8 custom scripting service math

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DreamFactoryTutorialsV8 custom scripting service math

You can create any number of custom 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 Custom Scripting Service.
  • Set the service name to 'math'.
  • Set the service label to 'Math'.
  • Go to the Config tab for the new service and set the Script Engine Type to V8js.
  • Set the Content to contain the following code then click Create Service.

var params, required, n1, n2, resource, result;

var lodash = require("lodash.min.js");

if (event.request.method !== "GET") {
    throw("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( "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"]};
    case "add":
        result = {"result": n1 + n2};
    case "subtract":
        result = {"result": n1 - n2};
    case "multiply":
        result = {"result": n1 * n2};
    case "divide":
        if (!n2) {
            throw("Divide by zero error.");
        result = {"result": n1 / n2};
        throw("Invalid or missing resource name.");

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. In this case 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 custom scripting service.