fleet/frontend

Fleet Front-End

The Fleet front-end is a Single Page Application using React with Typescript and Hooks.

Table of Contents

• Running the Fleet web app
• Directory Structure
• Deprecated
• Patterns
  • Typing
  • React Hooks (Functional Components)
  • React Context
  • Fleet API Calls
  • Page Routing
  • Other

Running the Fleet web app

For details instruction on building and serving the Fleet web application consult the Contributing documentation.

Directory Structure

Component directories in the Fleet front-end application encapsulate the entire component, including files for the component and its styles. The typical directory structure for a component is as follows:

└── ComponentName
  ├── _styles.scss
  ├── ComponentName.tsx
  ├── index.ts

• _styles.scss: The component css styles
• ComponentName.tsx: The React component
• index.ts: Exports the React component
  • This file is helpful as it allows other components to import the component by it's directory name. Without this file the component name would have to be duplicated during imports (components/ComponentName vs. components/ComponentName/ComponentName).

app_constants

The app_constants directory exports the constants used in the app. Examples include the app's URL paths, settings, and http statuses. When building features that require constants, the constants should be added here for accessibility throughout the application.

components

The component directory contains the React components rendered by pages. They are typically not connected to the redux state but receive props from their parent components to render data and handle user interactions.

context

The context directory contains the React Context API pattern for various entities. Only entities that are needed across the app has a global context. For example, the logged in user (currentUser) has multiple pages and components where its information is pulled.

interfaces

Files in the interfaces directory are used to specify the Typescript interface for a reusable Fleet entity. This is designed to DRY up the code and increase re-usability. These interfaces are imported in to component files and implemented when defining the component's props.

Additionally, local interfaces are used for props of local components.

layouts

The Fleet application has only 1 layout, the Core Layout. The Layout is rendered from the router and are used to set up the general app UI (header, sidebar) and render child components. The child components rendered by the layout are typically page components.

pages

Page components are React components typically rendered from the router. React Router passed props to these pages in case they are needed. Examples include the router, location, and params objects.

router

The router directory is where the react router lives. The router decides which component will render at a given URL. Components rendered from the router are typically located in the pages directory. The router directory also holds a paths file which holds the application paths as string constants for reference throughout the app. These paths are typically referenced from the App Constants object.

services

CRUD functions for all Fleet entities (e.g. query) that link directly to the Fleet API.

styles

The styles directory contains the general app style setup and variables. It includes variables for the app color hex codes, fonts (families, weights and sizes), and padding.

templates

The templates directory contains the HTML file that renders the React application via including the bundle.js and bundle.css files. The HTML page also includes the HTML element in which the React application is mounted.

utilities

The utilities directory contains re-usable functions and constants for use throughout the application. The functions include helpers to convert an array of objects to CSV, debounce functions to prevent multiple form submissions, format API errors, etc.

Deprecated

These directories and files are still used (as of 9/14/21) but are being replaced by newer code:

• fleet, now using services
• redux, now using services, local states, and various entities directly (e.g. React Router)
• Form.jsx Higher Order Component, now creating forms with local states with React Hooks (i.e. useState)

To view the deprecated documentation, click here.

Patterns

Typing

All Javascript and React files use Typescript, meaning the extensions are .ts and .tsx. Here are the guidelines on how we type at Fleet:

• Use global entity interfaces when interfaces are used multiple times across the app

• Use local interfaces when typing entities limited to the specific page or component

• Local interfaces for page and component props

  // page
  interface IPageProps {
    prop1: string;
    prop2: number;
    ...
  }
  
  // Note: Destructure props in page/component signature
  const PageOrComponent = ({
    prop1,
    prop2,
  }: IPageProps) => {
  
    return (
      // ...
    );
  };
  

• Local states

const [item, setItem] = useState<string>("");

• Fetch function signatures (i.e. react-query)

useQuery<IHostResponse, Error, IHost>(params)

• Custom functions, including callbacks

const functionWithTableName = (tableName: string): boolean => {
  // do something
};

React Hooks (Functional Components)

Hooks are used to track state and use other features of React. Hooks are only allowed in functional components, which are created like so:

import React, { useState, useEffect } from "React";

const PageOrComponent = (props) => {
  const [item, setItem] = useState<string>("");

  // runs only on first mount (replaces componentDidMount)
  useEffect(() => {
    // do something
  }, []);

  // runs only when `item` changes (replaces componentDidUpdate) 
  useEffect(() => {
    // do something
  }, [item]);
  
  return (
    // ...
  );
};

Note: Other hooks are available per React's documentation.

React Context

React Context is a store similar to Redux. It stores data that is desired and allows for retrieval of that data in whatever component is in need. View currently working contexts in the context directory.

Fleet API Calls

Deprecated:

Redux was used to make API calls, along with the fleet directory.

Current:

The services directory stores all API calls and is to be used in two ways:

• A direct async/await assignment
• Using react-query if requirements call for loading data right away or based on dependencies.

Examples below:

Direct assignment

// page
import ...
import queryAPI from "services/entities/queries";

const PageOrComponent = (props) => {
  const doSomething = async () => {
    const response = await queryAPI.load(param);
    // do something
  };
  
  return (
    // ...
  );
};

React Query

react-query (docs here) is a data-fetching library that gives us the ability to fetch, cache, sync and update data with a myriad of options and properties.

import ...
import { useQuery, useMutation } from "react-query";
import queryAPI from "services/entities/queries";

const PageOrComponent = (props) => {
  // retrieve the query based on page/component load
  // and dependencies for when to refetch
  const {
    isLoading,
    data,
    error,
    ...otherProps,
  } = useQuery<IResponse, Error, IData>(
    "query",
    () => queryAPI.load(param),
    {
      ...options
    }
  );

  // `props` is a bucket of properties that can be used when 
  // updating data. for example, if you need to know whether
  // a mutation is loading, there is a prop for that.
  const { ...props } = useMutation((formData: IForm) =>
    queryAPI.create(formData)
  );
  
  return (
    // ...
  );
};

Page Routing

Deprecated:

Redux was used to manage redirecting to different pages of the app.

Current:

We use React Router directly to navigate between pages. For page components, React Router (v3) supplies a router prop that can be easily accessed. When needed, the router object contains a push function that redirects a user to whatever page desired. For example:

// page
import PATHS from "router/paths";

interface IPageProps {
  router: any; // no typing in react-router v3
}

const PageOrComponent = ({
  router,
}: IPageProps) => {
  const doSomething = async () => {
    router.push(PATHS.HOME);
  };
  
  return (
    // ...
  );
};

Other

Local states

Our first line of defense for state management is local states (i.e. useState). We use local states to keep pages/components separate from one another and easy to maintain. If states need to be passed to direct children, then prop-drilling should suffice as long as we do not go more than two levels deep. Otherwise, if states need to be used across multiple unrelated components or 3+ levels from a parent, then the app's context should be used.

File size

The recommend line limit per page/component is 500 lines. This is only a recommendation. Larger files are to be split into multiple files if possible.