Typing Lists and Keys
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In React, lists are used to render multiple items. In TypeScript, you define the type of items inside the list, so each item has a clear structure.
Typing a List of Values
const items: string[] = ["Apple", "Banana", "Orange"];
Rendering a list:
items.map((item) => <li key={item}>{item}</li>);
- Each item is a string;
- Key helps React track elements.
Typing a List of Objects
type User = {
id: number;
name: string;
};
const users: User[] = [
{ id: 1, name: "Alex" },
{ id: 2, name: "John" },
];
Rendering object list:
users.map((user) => (
<li key={user.id}>{user.name}</li>
));
- Each item follows the
Usertype; - Use a unique key (like
id).
Define the type of list items, and use a unique key when rendering them.
すべて明確でしたか?
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セクション 1. 章 28
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Typing Lists and Keys
In React, lists are used to render multiple items. In TypeScript, you define the type of items inside the list, so each item has a clear structure.
Typing a List of Values
const items: string[] = ["Apple", "Banana", "Orange"];
Rendering a list:
items.map((item) => <li key={item}>{item}</li>);
- Each item is a string;
- Key helps React track elements.
Typing a List of Objects
type User = {
id: number;
name: string;
};
const users: User[] = [
{ id: 1, name: "Alex" },
{ id: 2, name: "John" },
];
Rendering object list:
users.map((user) => (
<li key={user.id}>{user.name}</li>
));
- Each item follows the
Usertype; - Use a unique key (like
id).
Define the type of list items, and use a unique key when rendering them.
すべて明確でしたか?
フィードバックありがとうございます!
セクション 1. 章 28