abdelrahman seada

Posted on Jul 15 • Updated on Sep 2

Stop rendering conditions like this

#javascript #webdev #programming #tutorial

we use conditions everywhere on our applications whether for state check or rendering some data into the view depending on some parameters. in this post will show some of how to render conditions in different way than using regular if(...) else {} blocks or even using ternary condition

for example (1)

type UserType = "admin" | "editor" | "user";

type User = { name: string; type: UserType };

const users: User[] = [
  { name: "john", type: "admin" },
  { name: "mike", type: "editor" },
  { name: "abdelrahman", type: "user" },
];

export default function Test() {
  const actions = ["create", "read", "update", "delete"];

  return (
    <div>
      {users.map((user) => (
        <div key={user.name}>
          {/* we need to render actions depending on user type */}
          <p>{user.name}</p>
          <div className="flex items-center">
            user actions:
            {user.type === "admin" && actions.map((a) => <Action a={a} key={a} />)}
            {user.type === "editor" && actions.filter((a) => a !== "create").map((a) => <Action a={a} key={a} />)}
            {user.type === "user" && actions.filter((a) => a === "read").map((a) => <Action a={a} key={a} />)}
          </div>
        </div>
      ))}
    </div>
  );
}

function Action(props: { a: string }) {
  const { a } = props;
  return <p className="px-2 py-1 border-[1px] mx-2 rounded-md">{a}</p>;
}

output for example (1)

in this example we had to make a check condition for each user type to render his actions, as you can see this consumes a lot of code , harder to debug , harder to add more in future lastly looks ugly but this is a better way to do so

example (2)

type UserType = "admin" | "editor" | "user";

type User = { name: string; type: UserType };

const users: User[] = [
  { name: "john", type: "admin" },
  { name: "mike", type: "editor" },
  { name: "abdelrahman", type: "user" },
];

const userActionsStates: Record<UserType, string[]> = {
  admin: ["create", "read", "update", "delete"],
  editor: ["create", "read", "update"],
  user: ["read", "update"],
};

export default function Test() {
  return (
    <div>
      {users.map((user) => (
        <div key={user.name}>
          {/* we need to render actions depending on user type */}
          <p>{user.name}</p>
          <div className="flex items-center">
            user actions:
            {userActionsStates[user.type].map((a) => (
              <Action key={a} a={a} />
            ))}
          </div>
        </div>
      ))}
    </div>
  );
}

function Action(props: { a: string }) {
  const { a } = props;
  return <p className="px-2 py-1 border-[1px] mx-2 rounded-md">{a}</p>;
}

output for example (2)

output is the same as example (1)

key changes

grouping each user type in object key and value should be what ever you want to render
in this case we pass each user type actions like the following

and here instead of rendering each condition like example (1) or making a ternary condition we get user actions from grouped object userActionsStates and just render whatever in the key's value and Voilà it's only one line of code

what about `else` ? what if we pass a user type that does not exists in the object ?

in this case we can add a default key in the object , this key will be used in false or undefined cases
like the following :


const userActionsStates : Record<UserType , string[] > = {
    admin: ["create", "read", "update", "delete"],
    editor: ["create", "read", "update"],
    user: ["read", "update"],
    default : ["read"]
}

if we updated users with new user that it's type is not defined like the last user object

then we will make a small change to the render method

<div className="flex items-center">
  user actions:
  {(userActionsStates[user.type] ?? userActionsStates["default"]).map((a) => (
    <Action key={a} a={a} />
  ))}
</div>

using null coalescing ?? we ensure that it will render as expected on
all conditions. :)

please note

using this method you can render anything in the key's value string , number , array , Component , ...etc.

summary

easy to read , debug and update 🧑‍💻
looks cool 😌
less code

it's up to your creativity and imaginations 💡🔥

Top comments (52)

Shrijal Acharya • Jul 17 • Edited

Just one simple piece of advice: Instead of using 4 spaces for indentation in code snippets for blogs, I think it's better to use 2 spaces as it reduces the need for horizontal scrolling.

Great read. 👌

abdelrahman seada • Jul 17

thanks for this advice 🤍

bop • Jul 19

github.com/gvergnaud/ts-pattern

this is also a good alternative

abdelrahman seada • Jul 19

will try it thanks 💕

Alexander Morgun • Aug 29

As always, all gold is in comments :)

Shahadat Hossain • Oct 8

I think this is not a matter of condition. It's a matter of good practice. Example 1 is easy to understand for beginners, but the other one is good to maintain and easy to extend.