<-- /notes<-- /notes/advanced-react-and-graphql

Form Handling

If you have a series of input items which will be sending a request to a backend, you can do a neat trick to prevent the user from modifying the data before the request has resolved. If you wrap eht inputs in a <fieldset> they will operate the same as usual. Then, whilst your request is firing, use your loading flag as a boolean attribute:

  <fieldset disabled={loading} aria-busy={loading}>
    // rest of component's inputs

The entire form will be greyed out while awaiting the response, and you can even style it differently using the aria-busy accessibility label:

&[aria-busy='true'] {
  /* blah blah blah */

Image Handling

In some situations, it might be easier to have a dedicated service to store your images so that they load faster, and can be easily manipulated when saved to disk. One of the more popular services for such a thing is known as Cloudinary which was used for building out this application, but the flow, (even if done locally, is largely the same).

When the user uploads an image through their browser, you're going to hit up the endpoint, with whatever parameters you need, and await the response containing the CDN link to the image. Then store that in your state and go about the rest of your application's processes (i.e. saving to a database, creating an item, etc). You may wonder why this is done whenever the <input type="file" /> is changed and it really doesn't need to be. You can do this just before submit so that you don't save excess to your database. I like this way because you can do things like revert to previously uploaded photos and display a preview super fast.

The following shows how to set-up with Cloudinary, given you have set up an account with an upload_preset (used for manipulation on upload):

uploadFile = async e => {
    const [file] = e.target.files // Take only the first file
    const data = new FormData()
    data.append('file', file)
    // Select the correct Cloudinary upload-preset configuration
    data.append('upload_preset', 'sick-fits') //sick-fits is specific to this application
    await this.setState({ uploading: true })
    const res = await fetch(imageEndpoint, {
      method: 'POST',
      body: data
    const upload = await res.json()
      image: upload.secure_url,
      uploading: false

The imageEndpoint depends on the provider you use, but for the most part, appending data to the body the request, and using the built in fetch, and FormData APIs, is the way to go.

Side Effects in Next.js

Occasionally you might need to perform what are commonly referred to as side-effects when handling certain situations in your application. Side effects are scenarios in which you are writing code that will reach out of its conventional scope to modify another part of the application, and generally, these guys are frowned upon by developers. Thing is, there are some snazzy advantages to these guys that can result in a better user experience, things like:

  • Live updating favicons
  • Modifying font imports
  • Changing the page title

A lot of these can be modified by changing what's contained in the <head> tag of your HTML page. Cool thing tho, since next is built, rather than parsed, it can allow you to use the <Head> tag imported from next/head anywhere in the application, and once built it will be surfaced into the actual head! That means you can overwrite certain parts of the head at lower levels in your application really easily:

// ...
import Head from 'next/head'

const SingleItem = ({ item }) => (
      <title> My App | {item.title}</title>
    <img src={item.largeImage} alt={item.title} />
    <div className="details">
      <p> {item.description}</p>
// ...

Testing Tips

If you are testing frontend components, a useful tip is to tag elements you'll need to test with a data-attribute, like data-test. That way, when you use a query selector in the test, you can fetch that element that much easier, and it's helpful to see what elements are being tested:

// Form.js
const Form = (props) => (
    <div data-test="form-wrapper" {...props}>
// Form.test.js
const wrapper = mount(<Form />)
const formWrapper = wrapper.find('div[data-test="form-wrapper"]')
// Test the formWrapper element...