Utilities

Similar to dependencies and configurations, utility functions can also be added to your project. These are not dependencies, but rather functions that you can use in your project. For example, you can create a function that returns the current date and time, or a function that returns the current user's name. Utilities are often placed to a separate folder called utils.

tree --dirsfirst
.
├── config
|   └── etaConfig.js
├── controllers
│   ├── authController.js
│   ├── mainController.js
│   └── todoController.js
├── services
│   ├── sessionService.js
│   ├── todoService.js
│   └── userService.js
├── middlewares
│   └── middlewares.js
├── templates
│   ├── login.eta
│   ├── main.eta
│   ├── registration.eta
│   ├── todo.eta
│   └── todos.eta
├── utils
|   └── ...
├── app.js
├── app-run.js
└── deps.js

As an example of a utility function that could be useful, let's create a function that can be used to render a given view template with data and the user from session, if the user exists. Let's call the function htmlWithUser, and place the function into a file called renderUtils.js, which is placed to the folder utils.

To be able to render a view template with data and the user from the session, the function needs the context, the name of the view template, and the data. Thus, the function receives the three parameters.

import { eta } from "../config/etaConfig.js";

const htmlWithUser = async (c, viewTemplate, data) => {
  // ...
}

export { htmlWithUser };

In the following, we assume that the application uses the addUserToContextMiddleware, which adds the user from the session to the context. If this would not be in use, we'd need to use the getUserFromSession function from the sessionService.js.

The implementation would be such that if the function is not given any data as a parameter, we'll start with an empty object as the data. After this, we set the property user of the data using the user from the context.

import * as sessionService from "../services/sessionService.js";
import { eta } from "../config/etaConfig.js";

const htmlWithUser = async (c, viewTemplate, data) => {
  data = data || {};
  data.user = c.user;

  // ...
};

export { htmlWithUser };

Finally, we render the given view template with the data, and return it as a response. Such a utility function would look as follows.

import * as sessionService from "../sessionService.js";
import { eta } from "../config/etaConfig.js";

const htmlWithUser = async (c, viewTemplate, data) => {
  data = data || {};
  data.user = c.user;
  return c.html(eta.render(viewTemplate, data));
};

export { htmlWithUser };

Now, with such a utility function, we could adjust our mainController.js to match the following.

import { htmlWithUser } from "../utils/renderUtils.js";

const showMain = async (c) => {
  return await htmlWithUser(c, "main.eta");
};

export { showMain };