Forem: Derek Nguyen

A spread argument must either have a tuple type or be passed to a rest parameter. ts(2556)

Derek Nguyen — Fri, 09 May 2025 23:09:52 +0000

You want to pass variable args to a function, like so:

const doSomething = (a: string, b?: string, c?: string): void => {};

However, TS didn't like it...

// não bom
const args = [['a', 'b', 'c'], ['a', 'b'], ['a']];
args.forEach((arg) => {

                // A spread argument must either
                // have a tuple type or be passed 
                // to a rest parameter. ts(2556)
                vvvvvv
    doSomething(...arg);
})

The problem is that doSomething expects one to three arguments of type string, but arg is typed as string[]. We need to narrow the type down, to match the arguments of doSomething()

// bom
const properTypedArgs: [a: string, b?: string, c?: string][] = [['a', 'b', 'c'], ['a', 'b'], ['a']];
properTypedArgs.forEach((arg) => {
    doSomething(...arg);
})

This works, but if you don't fancy re-typing the function's argument type defs or don't have it handy, TS utility type got you covered:

// ainda melhor
const properTypedArgs: Parameters<typeof doSomething>[] = [['a', 'b', 'c'], ['a', 'b'], ['a']];
properTypedArgs.forEach((arg) => {
    doSomething(...arg);
})

That's all!

TS playground
Parameter<>
typeof

'Ascending' server environment variables to client with Vite

Derek Nguyen — Tue, 24 May 2022 07:24:52 +0000

TL;DR:

// vite.config.js
{
  envPrefix: ['VITE_', 'CF_PAGES_'],
}

With Vite, we can set environment variables in a .env, .env.{mode}, or .env.{mode}.local:

SECRET_STUFF          = "only for server"
VITE_NOT_SECRET_STUFF = "for server and client"

The default VITE_ prefix will pass the variables to the client and we can use it with a string:

// in a client js file
let msg = `Hey {import.meta.env.VITE_NAME}`

But what if we want to 'ascend' an env set by the platform? In my case, I want to expose CF_PAGES_URL, which contains the preview url for my Cloudflare Pages build. Obviously I can't write it in .env... I have read somewhere that .env can access other variables with a syntax like

VITE_PAGES_URL=$CF_PAGES_URL

...but I haven't tried that, because I found this solution:

// vite.config.js
{
  envPrefix: ['VITE_', 'CF_PAGES_'],
}

That would 'ascend' all the CF_PAGES_ variables & allow me to use them client side.

The end.

Netlify redirects with query params don't work? Check shadowing

Derek Nguyen — Tue, 25 Jan 2022 15:18:03 +0000

I want to redirect from this url...

https://example.com/page?id=abc

To this:

https://example.com/page/abc

Netlify allows you to redirects based on query params, hooray! Here's an example from the docs:

/store id=:id  /blog/:id  301
# /store?id=my-blog-post to /blog/my-blog-post with a 301 redirect

So, this would just work, right?

/page id=:id  /page/:id 301

No. No it wouldn't.

It turns out 'shadowing' is a thing. In short, Netlify won't accept the rule if there's already a static asset at the target address.

# working
/page id=:id  /page/:id 301!

This baffles me a little bit, because supposedly, 301 is the default rule and these all works fine:

# /b is a static page
/a   /b

Also, seeing Netlify being mostly known as a static site host, I'd expect redirecting into existing static pages would be the majority of the cases.

Anyway, I wasted 30' on this... should I have just learn to read the docs better? Maybe. At least I hope this helped other fellows who can't read docs.

How to use SVGs in React

Derek Nguyen — Fri, 05 Nov 2021 17:43:48 +0000

This article will explore how to use SVG in React in three examples:

A loading icon
A hover text effect
A pizza customizer

SVG is an incredible format. Not only is it a lightweight, infinitely scalable alternative to raster images, it can also be styled, animated with CSS when embedding inline in HTML. SVGs can be used everywhere:

icons, animated icons
favicons
special text effects
a lightweight blurred placeholder for lazy-loaded images
data visualization
3d graphics

How to use SVG in React

There are a few ways to use an SVG in a React app:

Use it as a regular image
Import it as a component via bundler magic (SVGR)
Include it directly as JSX

Let's quickly go over each of them.

Use SVGs as regular images

SVGs can be used as an image, so we'd treat them as any other image resource:

<img src="/path/to/image.svg" alt="SVG as an image">

Note: A few meta frameworks handle this out-of-the-box, such as Gatsby & Create React App.

In Webpack 5, this is (surprisingly) simple to setup. Parcel 2 handles this out of the box with a special import prefix. Rollup has an official plugin.
import mySvg from './path/to/image.svg'

Pros:

Straightforward

Cons:

SVG can't be customized

Use case: Simple replacement for raster images that don't need customization, e.g., logos.

Import SVGs as components via bundler magic

When importing an SVG as a component, we can inline SVGs directly in our markup & use them as a component.

import { ReactComponent as IconMenu } from './icons/menu.svg'

export const ButtonMenu = ({ onClick }) => {
  return (
    <button onClick={onClick}>
        <span>Open Menu</span>
        <IconMenu width="1rem" />
    </button>
  )
}

SVGR is the library that powers this ability. Setting it up could be a little hairy, thankfully many popular frameworks (Create React App, Gatsby) support this feature out of the box.

Pros:

Easy to handle a large amount of SVG
Powerful templating

Cons:

May need additional configuration
Writing React component template is not straightforward

Use case: A custom SVG icon library

Include SVGs directly in JSX

JSX supports all SVG tags. We can (almost) paste the SVG directly into our React components!

This is the most straightforward method to take full advantage of SVG without bundler support, which is why we will use this method for all of our examples later in this article.

The only gotcha is that instead of regular HTML attributes, we have to use JS property syntax, e.g stroke-width -> strokeWidth

// fun fact: `viewBox` has always been camel-cased.
export const LoadingIcon = () => {
  return (
    <svg
      viewBox="0 0 24 24"
      xmlns="<http://www.w3.org/2000/svg>"
    >
      <path strokeWidth="2" stroke="tomato" d="M10...">
    </svg>
  )
}

Pros:

Straightforward

Cons:

Depending on the SVG, component code may not readable
Not scalable for a large number of SVGs

Use case: One-off graphic such as illustration, blog header

SVGs & React in practice

This article will not be completed if we don't at least show off a few SVG tricks. In the following examples, we will explore what makes SVGs awesome.

Prerequisite

All examples will use create-react-app (CRA) and CSS Module. A way to start a CRA project is using codesandbox. Otherwise, make sure Node is installed (any TLS versions will do) and run this:

npx create-react-app my-app && cd my-app

Example 1: A Loading Icon

Here's what we'll be making:

Let's try writing this SVG from scratch. All we need is one circle. This is the SVG in its entirety:

const LoadingIcon = () => {
  return (
    <svg
      viewBox="0 0 24 24"
      xmlns="<http://www.w3.org/2000/svg>"
    >
      <circle
        cx="12" cy="12" r="8"
        stroke-width="4" stroke="tomato"
        fill="none"
      />
    </svg>
  )
}

Now let's make it move! We can now attach class names to SVG elements and animate them with CSS transform & animation.

Animating paths is a classic SVG trick, and it's all about stroke-dasharray. This property creates dashed lines, like in the image below:

Nothing too exciting. However, things get more interesting when you realize that these dashes can be offset. What if, instead of many short dashes, we have a single dash whose length is the same as the circle's circumference? We can then move that dash around by changing the offset, giving the appearance that the path is being shortened or lengthened.

Let's give it a try:

.main {
  stroke-dasharray: 50;
  stroke-dashoffset: 0;
  animation: load 5s linear infinite;
  transform-origin: center;
}

@keyframes load {
  0% {
    stroke-dashoffset: 50;
  }
  50% {
    stroke-dashoffset: 0;
  }
  100% {
    stroke-dashoffset: -50;
  }
}

Setting stroke-dashoffset to a negative value pushes the path further down & create the looping effect.

Note: 50 is roughly the circumference of the circle and for our use case we don't ever need to change that value. In other cases, we might need to calculate the exact number:
const $circle = document.querySelector('.main')
const radius = $circle.r.baseVal.value
const circumference = Math.PI * 2 * radius

Finally, to make the animation more dynamic, let's also rotate the circle.

@keyframes load {
  0% {
    transform: rotate(0deg);
    stroke-dashoffset: 50;
  }
  50% {
    stroke-dashoffset: 0;
  }
  100% {
    transform: rotate(360deg);
    stroke-dashoffset: -50;
  }
}

prefers-reduced-motion

Loading icons typically doesn't have the type of animations that could cause issues. However, for a larger graphic with lots of animation, it's a good practice to provide a more gentle animation. In our case, we can extract the animation duration into a CSS variable & define a larger value inside of the prefers-reduced-motion media tag.

/* simple-icon.module.css */

.svg {
  /* ... */
  --speed: 5s;
}

@media (prefers-reduced-motion: reduce) {
  .svg {
    --speed: 10s;
  }
}

.path {
  /* ... */
  animation: load var(--speed, 5s) linear infinite;
}

Customize with React

Now let's make the icon customizable. We want to allow users to change color & thickness.

import styles from "./simple-icon.module.css";

export const SimpleLoadingIcon = ({
  color = "currentColor",
  thickness = 2
}) => (
  <svg
    className={styles.svg}
    viewBox="0 0 24 24"
    xmlns="<http://www.w3.org/2000/svg>"
  >
    <circle
      className={styles.path}
      cx="12"
      cy="12"
      r="8"
      strokeLinecap="round"
      strokeWidth={thickness}
      stroke={color}
      fill="none"
    />
  </svg>
);

If color is unset, the stroke color will inherit from its parent.

Accessibility

Since our loading icon does not contain any text, we should give it a

so a screen reader can make sense of it. To dive deeper into accessibility with SVGs, CSS Tricks cover this topic extensively.

<svg aria-labelledby="svg-icon-loading">
  <title id="svg-icon-loading">Loading</title>
  ...
</svg>

Now that we have a title, a tooltip will show up when the cursor hovers over the SVG. If that seems unnecessary, we can get rid of it by adding pointer-events: none to SVG's style.

Result

And with that, we can now use this loading icon anywhere! This demo below contains a slightly more complex version of the icon above.

Example 2: Special Text Effect

SVG can do wild things with text, but let's start with something simple. Like the previous example, we will start with just the SVG and then bring things up a notch with React.

The graphic we'll be working with is rather long, but here's the main parts:

const Graphic = () => {
  return (
    <svg viewBox="0 0 600 337">
      <defs>
        <linearGradient id="gradient"> /* ... */
        </linearGradient>
      </defs>

      <text x="20" y="1.25em">
        <tspan>Using SVGs</tspan>
        <tspan x="20" dy="1em">in React</tspan>
      </text>
    </svg>
  )
}

SEO Concerns

We can nest this SVG inside heading tags. It is valid HTML (test it with the w3c validation tool) and screen readers can pick up the text inside.

SVG assets

Let's look at the parts. <defs> is SVG's compartment where we can put stuff for later use. That can be shapes, paths, filters, and gradients, such as in the SVG above. True to the compartment analogy, browsers will not render elements placed inside a <def> block.

If we want to apply the defined gradient to the text object, we can reference its id with the following syntax:

<text x="20" y="1.25em" fill="url(#gradient)">
  <tspan>Using SVGs</tspan>
  <tspan x="20" dy="1em">in React</tspan>
</text>

Sweet! But we can achieve this effect in modern CSS as well. So let's see what else SVG can do.

Creating outline text is relatively easy with SVG: just change fill to stroke, and the gradient will still be applied.

<text x="20" y="1.25em" stroke="url(#gradient)">
  <tspan>Using SVGs</tspan>
  <tspan x="20" dy="1em">in React</tspan>
</text>

And better yet, that gradient can be animated.

Try to do that, CSS!

The syntax for creating SVG gradient animation is quite verbose, unfortunately.

<linearGradient id="gradient" x1="50%" y1="0%" x2="50%" y2="100%">
  <stop offset="0%" stop-color="plum">
    <animate
      attributeName="stop-color"
      values="plum; violet; plum"
      dur="3s"
      repeatCount="indefinite"
    ></animate>
  </stop>

  <stop offset="100%" stop-color="mediumpurple">
    <animate
      attributeName="stop-color"
      values="mediumpurple; mediumorchid; mediumpurple"
      dur="3s"
      repeatCount="indefinite"
    ></animate>
  </stop>
</linearGradient>

Let's make something even cooler. How about this XRay hover effect?

The trick here is to use text as a clipping path. We can then animate a circle clipped inside the text as we move the cursor in React.

We'll create a new element called clip-path (clipPath in JSX land) in <defs>, and place <text> into it. This serves two purposes: so we can (1) use the text as a mask and (2) clone it to create the outline effect by using <use>.

<svg>
  <defs>
    <clipPath id="clip-text">
      <text id="text" x="20" y="1.25em">
        <tspan>Using SVGs</tspan>
        <tspan x="20" dy="1em">
          in React
        </tspan>
      </text>
    </clipPath>
  </defs>
  {/* this circle visible to viewer. */}
  <circle ... />

  <use href="#text" stroke="url(#gradient)" />

  {/* this circle is clipped inside the text. */}
  <g clipPath="url(#clip-text)">
    <circle ... />
  </g>
</svg>

So far, we've been using url(#id) to refer to gradients & clipping paths placed inside of the <defs> block. For shapes and text, we'll need to use a tag: <use>, and the syntax is slightly different:

<use href="#id" stroke="..." fill="..." />

The referenced text can still be customized by adding attributes to the use tags. <use> is really cool & we'll see in the last example how it can be used to nest external SVGs.

SVG's coordinate systems

One of the pain points of using SVG is its coordinate system. If we naively implement the function like this:

window.addEventListener('mousemove', (e) => {
  $circle.setAttribute('cx', e.clientX)
  $circle.setAttribute('cy', e.clientY)
})

We'll quickly find out that the cursor position does not match up with the circle inside the SVG. The circle's unit is relative to its containing SVG's viewBox.

For this reason, we'll implement a simple script that'll translate the position correctly.

const svgX = (clientX - svgElementLeft) * viewBoxWidth / svgElementWidth
const svgY = (clientY - svgElementTop) * viewBoxHeight / svgElementHeight

Move the circle with React

We'll need to move two circles, so let's attach some refs.

import { useRef, useEffect } from "react";

export const Graphic = () => {
  const innerCircleRef = useRef(null)
  const outerCircleRef = useRef(null)

  useEffect(() => {
    const $innerCircle = innerCircleRef.current
    const $outerCircle = outerCircleRef.current
    if (!$innerCircle || !$innerCircle) return

    const handleMouseMove = (e) => {
      const { clientX, clientY } = e
      /* Translate coordinate from window to svg, omitted for brevity */
      const [x, y] = translateCoords(clientX, clientY)
      $innerCircle.setAttribute('cx', x)
      $innerCircle.setAttribute('cx', y)
      $outerCircle.setAttribute('cx', x)
      $outerCircle.setAttribute('cx', y)
    }

    window.addEventListener("mousemove", handleMouseMove)
    return () => {
      window.removeEventListener("mousemove", handleMouseMove)
    }
  })

  return (
    <svg>
      {/* ... */}
      <circle ref={outerCircleRef} />
      {/* ... */}
      <g clipPath="url(#text)">
        <circle ref={innerCircleRef} />
      </g>
    </svg>
  )
}

Note: the code for translating position has been omitted for clarity. See the codesandbox below for a complete source.

Result

Check out the final product in this Codesandbox demo. See if you can find a hidden message!

Example 3: Pizza Customizer

In this example, let's explore how we can compose an SVG on the fly with React! A local pizzeria knocks on the door and asks if we could build them a fun graphic for their online ordering site. Of course, we say yes.

Prerequisite

We'll need Sanity Studio for this example. Let's use the following structure:

pizza-sanity
  ├── frontend <create-react-app>
  └── studio <sanity studio>

Follow the steps below to install & initiate a new create-react-app project:

cd frontend
npx create-react-app .

While waiting for the script to load, let's initiate the studio:

cd ../studio
npm install -g @sanity/cli
sanity init
# after signing in, answer the questions as below
? Select project to use 
❯ Create new project
? Your project name
❯ Sanity Pizza
? Use the default dataset configuration?
❯ Yes
? Project output path
❯ /Users/me/Documents/sanity-pizza/studio
? Select project template
❯ Clean project with no predefined schemas

When that's all done, we'll also want to add CRA's development host to the project's CORS allowed list.

sanity cors add http://localhost:3000 --credentials

See the getting started guide for further information. If you'd like a reference, see the project on Github.

Writing the schema

Toppings can be placed on different pizzas, so we could have two types of documents: toppings and pizzas, containing many other toppings.

Sanity allows us to create schema in code, making it powerful & flexible, but simple to get started. In schemas directory, create a new files:

/* schemas/pizza.js */

export const topping = {
  type: 'document',
  name: 'topping',
  title: 'Topping',
  fields: [
    {
      title: 'Title',
      name: 'title',
      type: 'string',
      validation: Rule => Rule.required().min(2),
    },
    {
      title: 'SVG',
      name: 'svg',
      type: 'text',
      validation: Rule => Rule.required().min(2),
    },
    fieldSize,
  ],
}

export const pizza = {
  type: 'document',
  name: 'pizza',
  title: 'Pizza',
  fields: [
    {
      title: 'Title',
      name: 'title',
      type: 'string',
      validation: Rule => Rule.required(),
    },
    {
      title: 'Base Pizza',
      name: 'svg',
      type: 'text',
      validation: Rule => Rule.required(),
    },
    fieldSize,
    {
      title: 'Toppings',
      name: 'toppings',
      type: 'array',
      of: [{
        type: 'reference',
        to: [{ type: topping.name }]
      }],
      validation: Rule => Rule.required().min(2),
    }
  ]
}

Note that inside of the pizza document type, we create an array of references to the available toppings.

For the topping itself, we create a text field where editors can paste the SVG graphic.

Why not upload SVG as an image?
It's possible to reference external SVGs (and leverage browser cache!). However, it won't be stylable in CSS as inlined SVG. Depending on the use case, external SVG could be the better choice.

In Sanity Studio, there should be a schemas/schema.js file. Let's add the document types we've specified above.

import createSchema from 'part:@sanity/base/schema-creator'
import schemaTypes from 'all:part:@sanity/base/schema-type'
import { pizza, topping } from './pizza'

export default createSchema({
  name: 'default',
  types: schemaTypes.concat([
    topping,
    pizza
  ]),
})

Now that all the SVGs are placed in the Studio, it's time to build the React app. We'll use picosanity, a smaller Sanity client.

npm i picosanity

Make a client.js file and create the Sanity client:

import PicoSanity from 'picosanity'

export const client = new PicoSanity({
  projectId: '12345678',
  dataset: 'production',
  apiVersion: '2021-03-25',
  useCdn: process.env.NODE_ENV === 'production',
})

Then we can import it into our React app and use it to fetch data. For simplicity, let's fetch in useEffect and store the data inside of a useState.

import { useState, useEffect } from 'react'
import { client } from './client'

const App = () => {
  const [data, setData] = useState(null)
  useEffect(() => {
    const getPizzaData = () => {
      client.fetch(`
        *[_type == "pizza"] {
          ...,
          toppings[] -> {
            _id,
            title,
            svg,
            size,
          }
        }
      `)
    }

    getPizzaData.then(data => setData(data))
  })

  return ( /* ... */ )
}

This will yield the following data:

[
  {
    _id: "2b2f07f0-cfd6-4e91-a260-ca30182c7736",
    _type: "pizza",
    svg: "<svg ...",
    title: "Pepperoni Pizza",
    toppings: [
      {
        _id: "92b5f3f1-e0af-44be-9575-94911077f141",
        svg: "<svg ...",
        title: 'Pepperoni'
      },
      {
        _id: "6f3083f3-a5d5-4035-9724-6e774f527ef2",
        svg: "<svg ...",
        title: 'Mushroom'
      },
    ]
  }
]

Let's assemble a pizza from the topping SVG and the pizza's base SVG. This is where <symbol> comes in handy.

export const Pizza = ({ data }) => {
  const { _id, svg: baseSvg, toppings } = data
  return (
  <svg>
    {/* create a symbol for each topping */}
    {toppings.map(({ _id: toppingId, svg }) => (
      <symbol key={toppingId} id={toppingId} dangerouslySetInnerHTML={{ __html: svg }} />
    ))}

    <g dangerouslySetInnerHTML={{ __html: baseSvg }} />
    {/* use them */}
    {toppings.map(({ _id: toppingId }) => {
      return (
        <use key={_id} href={`#${toppingId}`} />
      )
    })}
  </svg>
  )
}

Symbols are hidden by default and can be created with <use>. We can still apply transform as with a standard SVG element. This is also how SVG sprite works.

Add customizer

We'll add a slider for each topping and once again simply use useState to store users' inputs in an object.

import { useState } from 'react'

export const Pizza = ({ data }) => {
  const { _id, svg: baseSvg, toppings } = data
  const [ config, setConfig ] = useState({})
  const handleChangeFor = (toppingId) => (value) => {
    setConfig(config => ({
      ...config,
      [toppingId]: value
    }))
  }

  return (
    <section>
      <svg>{ /* ... */ }</svg>
      <form>
        {toppings.map(topping => (
          <div key={topping._id}>
            <label htmlFor={topping._id}>{topping.title}</label>
            <input
              type="range"
              value={config[topping._id] || 0}
              onChange={handleChangeFor(topping._id)}
            />
          </div>
        ))}
      </form>
    </section>
  )
}

Randomizer

The most challenging part of this exercise is placing the toppings on top of the pizza. It turns out that just placing each topping at a random position does not create a very appetize-looking pizza!

We want to place the toppings evenly. Thankfully geometry nerds have already figured this out ages ago! Vogel spiral to the rescue. Read more about it here.

So far, so good. Let's give each topping a random rotation and vary its scale slightly, so the pizza looks more natural.

However, as soon as we add the transformation, the pizza becomes a mess. Here's what we're missing: instead of rotating from the center of itself, each topping's SVG is rotating from the center of its containing SVG (the pizza.) To fix this, we need to add the following CSS to each use element:

use {
  transform-origin: center;
  transform-box: fill-box;
}

Note: The order of transformation matter. We have to apply translate before scale or rotate to keep the SVG in the intended position.

With that, we now have a decent pizza customizer!

Animate with react-spring

So far, we've been relying on CSS for animation, but CSS can only take us so far. Let's create an animation where toppings fall onto the pizza whenever users update their order.

Let's use react-spring to create a simple animation.

Note: using hook throws an error with <use/> for some reasons, so I'm using react-spring's render props API instead.

npm i react-spring

Now it's a good time to extract into its component & add the animation there.

import { Spring, config } from 'react-spring/renderprops'

export const UseTopping = ({
  size,
  toppingId,
  x,
  y,
  i,
  rotation,
  scale
}) => {
  return (
    <Spring
      from={{ y: y - 40, opacity: 0 }}
      to={{ y, opacity: 1 }}
      delay={i * 15}
      config={config.wobbly}
    >
      {props => <use
        className={styles.topping}
        href={`#${toppingId}`}
        opacity={props.opacity}
        style={{
          transform: `
            translate(${x}px, ${props.y}px)
            scale(${scale})
            rotate(${rotation}deg)
          `
        }}
      />}
    </Spring>
  )
}

Result

Play with the final demo here! The source code is available on Github.

d4rekanguok / sanity-pizza

Wrapping Up

We haven't scratched the surface of SVG coolness. However, SVG is not without flaws:

Verbose syntax
Texts inside SVG do not flow like in HTML. Break text manually into works for one-off graphics, but it is not scalable.
Position & coordinate could be tricky
When animating complex SVGs, performance could be an issue

However, SVGs can enrich our React websites and applications with little effort with the right use case.