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A Guard is a security layer on top of a Worker in Fort.js, meaning it is called after the controller is initiated. It controls whether a request should be allowed to call the controller methods or worker.

Use Cases

  • Data validation at the method level.
  • Authentication at the controller method level.
  • Performing tasks and passing them to the Worker.

Multiple Guards

Multiple guards can be assigned to a Worker, and they are called in the same order as declared.

Guard members

A guard has following member -

Creating a Guard

A Guard is a class that extends the Guard class from Fort.js. It has a check method as its lifecycle.

Lifecycle Method

The check method can perform various tasks, such as validation, and return the result. It can return two types of data:

  1. null - It means the guard has passed the request.
  2. HTTP response - It means the guard has rejected the request. The HTTP response is directly returned to the user.

Explore the powerful capabilities of Guards by implementing them in your Fort.js application.


Let's create a Guard that validates user data sent in the HTTP body. It will allow the request to proceed if the user is valid and reject it otherwise.

import { Guard, HttpResult, MIME_TYPE, HTTP_STATUS_CODE } from "fortjs";
import {isEmail, isLength, isIn} from "validator";

export class ValidUserGuard extends Guard {

async check() {
const user = { // extracted the info from request body
gender: this.body.gender,
address: this.body.address,
emailId: this.body.emailId

const errMsg = this.validate(user);

if (errMsg == null) {

// pass user to worker method, so that they dont need to parse again = user;

return null; // Guard allows the request to pass

} else {
return textResult(errMsg, HTTP_STATUS_CODE.BadRequest);

validate(user) {
let errMessage;
if ( == null || !isLength(, 5)) {
errMessage = "name should be minimum 5 characters"
} else if (user.password == null || !isLength(user.password, 5)) {
errMessage = "password should be minimum 5 characters";
} else if (user.gender == null || !isIn(user.gender, ["male", "female"])) {
errMessage = "gender should be either male or female";
} else if (user.gender == null || !isEmail(user.emailId)) {
errMessage = "email not valid";
} else if (user.address == null || !isLength(user.address, 10, 100)) {
errMessage = "address length should be between 10 & 100";
return errMessage;

Now you can use this guard on any controller method:

import { Controller, guards } from "fortjs";
import { ValidUserGuard } from "@/guards";

export class UserController extends Controller {

const user = ;


This guard will validate the user data before allowing the request to proceed to the addUser method in the UserController.


  • Guards enable the extraction of reusable logic such as validation and authentication.
  • Guards can be independently used by multiple controller methods, enhancing code reusability.
  • The use of guards contributes to cleaner code structures.
  • Guards can be independently unit-tested, ensuring reliability in isolation.