Typing Component Props
This is intended as a basic orientation and reference for React developers familiarizing with TypeScript.
Basic Prop Types Examples
A list of TypeScript types you will likely use in a React+TypeScript app:
type AppProps = {
message: string;
count: number;
disabled: boolean;
/** array of a type! */
names: string[];
/** string literals to specify exact string values, with a union type to join them together */
status: 'waiting' | 'success';
/** an object with known properties (but could have more at runtime) */
obj: {
id: string;
title: string;
};
/** array of objects! (common) */
objArr: {
id: string;
title: string;
}[];
/** any non-primitive value - can't access any properties (NOT COMMON but useful as placeholder) */
obj2: object;
/** an interface with no required properties - (NOT COMMON, except for things like `React.Component<{}, State>`) */
obj3: {};
/** a dict object with any number of properties of the same type */
dict1: {
[key: string]: MyTypeHere;
};
dict2: Record<string, MyTypeHere>; // equivalent to dict1
/** function that doesn't take or return anything (VERY COMMON) */
onClick: () => void;
/** function with named prop (VERY COMMON) */
onChange: (id: number) => void;
/** function type syntax that takes an event (VERY COMMON) */
onChange: (event: React.ChangeEvent<HTMLInputElement>) => void;
/** alternative function type syntax that takes an event (VERY COMMON) */
onClick(event: React.MouseEvent<HTMLButtonElement>): void;
/** any function as long as you don't invoke it (not recommended) */
onSomething: Function;
/** an optional prop (VERY COMMON!) */
optional?: OptionalType;
/** when passing down the state setter function returned by `useState` to a child component. `number` is an example, swap out with whatever the type of your state */
setState: React.Dispatch<React.SetStateAction<number>>;
};
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