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React with TypeScript Quiz

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Question 1/15

How do you enforce that a certain number of times a component rerenders when a particular prop changes in TypeScript?

class MyComponent extends React.Component<{ inputValue: number }> {
    componentDidUpdate(prevProps: { inputValue: number }) {
        if (prevProps.inputValue !== this.props.inputValue) {
            console.log('Rerendered!');
        }
    }
}

Select your answer

You don't directly enforce rerender times; React manages rendering based on prop or state changes.

Using state variables to count rerenders manually within the component.

By editing React's internal render processes (not recommended).

By writing a custom `shouldComponentUpdate` method that increments each time.

Question 2/15

How does TypeScript handle missing props when destructuring in a function component?

interface MyComponentProps {
    name: string;
    age?: number;
}

const MyComponent: React.FC<MyComponentProps> = ({ name, age = 0 }) => (
    <div>{name}, {age}</div>
);

Select your answer

By setting default values during destructuring or marking props as optional.

By throwing a compile-time error.

By ignoring missing values without warning.

By setting all destructured values to `null`.

Question 3/15

Which hook is used to set up initial state in a TypeScript functional component?

const [count, setCount] = useState<number>(0);

Select your answer

useState

useContext

useReducer

useEffect

Question 4/15

How can you share state between two React components without passing props explicitly?

const MyContext = React.createContext<{value: string, setValue: React.Dispatch<React.SetStateAction<string>>} | undefined>(undefined);

const MyProvider: React.FC = ({ children }) => {
    const [value, setValue] = useState("");
    return <MyContext.Provider value={{ value, setValue }}>{children}</MyContext.Provider>;
};

const ComponentA: React.FC = () => {
    const context = React.useContext(MyContext);
    return context ? <button onClick={() => context.setValue('Hello')}>Change</button> : null;
};

const ComponentB: React.FC = () => {
    const context = React.useContext(MyContext);
    return context ? <div>{context.value}</div> : null;
};

Select your answer

Creating a global object to store state.

Developing a custom hook that returns props.

Utilizing local storage for state persistence.

Using React's Context API to manage shared state.

Question 5/15

In TypeScript, how do you prevent assigning `undefined` to a prop?

interface MyComponentProps {
    name: string;
}

const MyComponent: React.FC<MyComponentProps> = ({ name }) => {
    return <div>Hello, {name}</div>;
};

Select your answer

With default parameters in the function implementation.

By initializing the prop with an empty string.

By using `undefined` in the type restriction.

By not using the `?` modifier in the interface declaration.

Question 6/15

How can you ensure a component in TypeScript only accepts props of a specific shape using TypeScript?

interface ButtonProps {
    label: string;
    onClick: () => void;
}

const Button: React.FC<ButtonProps> = ({ label, onClick }) => (
    <button onClick={onClick}>{label}</button>
);

Select your answer

Use dynamic prop types with the `any` type.

Use `PropTypes` like in JavaScript React.

Directly declare types in the function body after JSX.

Use an interface to define the prop types and use it in the component type definition.

Question 7/15

Which TypeScript utility can you use to define only some of the properties of an interface as required?

interface Person {
    name: string;
    age: number;
    address?: string;
}

const person: Required<Pick<Person, 'name' | 'age'>> = { name: 'Alice', age: 30 };

Select your answer

`Partial` and `Omit` combined.

`Readonly` and `Mutable`.

`Optional` and `Strict`.

`Pick` and `Required` combined.

Question 8/15

In a TypeScript React component, how can you specify that a prop is optional?

interface MyComponentProps {
    name?: string;
}

const MyComponent: React.FC<MyComponentProps> = ({ name }) => {
    return <div>{name}</div>;
};

Select your answer

By using an `Optional` type alias.

By using `?` after the prop name.

By using `undefined` in the prop type.

By initializing the prop with `null`.

Question 9/15

Given the following TypeScript code, what type does the `setColor` function accept?

const [color, setColor] = useState<string | null>(null);

Select your answer

Either a string or null.

Only null values.

Only numbers.

Only strings.

Question 10/15

How do you define default props in a React component using TypeScript?

interface MyComponentProps {
    name?: string;
}

const MyComponent = ({ name = "Guest" }: MyComponentProps) => {
    return <div>Hello, {name}</div>;
};

Select your answer

Directly in the JSX return statement.

Using `MyComponent.defaultProps`.

Using `static defaultProps` in a class component.

Using default parameter syntax in the props destructuring.

Question 11/15

How can you extend interfaces in TypeScript when creating a React component?

interface BaseProps {
    id: string;
}

interface AdvancedProps extends BaseProps {
    date: Date;
}

const Component: React.FC<AdvancedProps> = ({ id, date }) => (
    <div>{id}: {date.toISOString()}</div>
);

Select your answer

By creating a utility type.

By using `implements` keyword.

By merging objects in the component.

By using the `extends` keyword.

Question 12/15

What is the purpose of the `React.FC` type in a TypeScript React component?

const MyComponent: React.FC = () => {
    return <div>Hello, World!</div>;
};

Select your answer

To type the props of a functional component.

To declare state in a functional component.

To handle side effects in a component.

To define a class component.

Question 13/15

What is the `key` prop used for in React lists?

const items = ['a', 'b', 'c'];

const listItems = items.map((item, index) => (
    <li key={index}>{item}</li>
));

Select your answer

To set a unique id for each HTML element.

To disable an item in a list.

To help React identify which items have changed in a list for efficient re-rendering.

To create a reference pointer for each element.

Question 14/15

How can you indicate that a functional component should only render after certain props are confirmed to be non-null and non-undefined?

const MyComponent: React.FC<{ title?: string }> = ({ title }) => {
    if (!title) {
        return null;
    }
    return <div>{title}</div>;
};

Select your answer

By enforcing non-null types at the TypeScript configuration level.

Through custom exception handling in JSX.

By checking the props directly and conditionally rendering a component.

By declaring prop types as `nonNullable` in TypeScript.

Question 15/15

How do you define a prop that accepts children in TypeScript with React?

interface MyComponentProps {
    children?: React.ReactNode;
}

const MyComponent: React.FC<MyComponentProps> = ({ children }) => {
    return <div>{children}</div>;
};

Select your answer

By defining the prop type as `Element`.

By defining the prop type as `ReactElement`.

By defining the prop type as `React.ReactNode`.

By defining the prop type as `JSX.Element`.

Your Results

You did not answer any questions correctly.

Your Answers

Question 1/15

😊 Your answer was correct 🙁 Your answer was incorrect

How do you enforce that a certain number of times a component rerenders when a particular prop changes in TypeScript?

class MyComponent extends React.Component<{ inputValue: number }> {
    componentDidUpdate(prevProps: { inputValue: number }) {
        if (prevProps.inputValue !== this.props.inputValue) {
            console.log('Rerendered!');
        }
    }
}

Available answers

You don't directly enforce rerender times; React manages rendering based on prop or state changes.

Using state variables to count rerenders manually within the component.

By editing React's internal render processes (not recommended).

By writing a custom `shouldComponentUpdate` method that increments each time.

React handles rerendering automatically based on changes in state or props. While you can observe when it happens, directly controlling the number of rerenders is not a typical pattern in React.

Question 2/15

😊 Your answer was correct 🙁 Your answer was incorrect

How does TypeScript handle missing props when destructuring in a function component?

interface MyComponentProps {
    name: string;
    age?: number;
}

const MyComponent: React.FC<MyComponentProps> = ({ name, age = 0 }) => (
    <div>{name}, {age}</div>
);

Available answers

By setting default values during destructuring or marking props as optional.

By throwing a compile-time error.

By ignoring missing values without warning.

By setting all destructured values to `null`.

TypeScript will require a default value in the destructuring if a prop marked as optional is missing, avoiding runtime errors by setting a default value.

Question 3/15

😊 Your answer was correct 🙁 Your answer was incorrect

Which hook is used to set up initial state in a TypeScript functional component?

const [count, setCount] = useState<number>(0);

Available answers

useState

useContext

useReducer

useEffect

The

useState

hook is used to set up local state in a functional component. You can specify the type using generics, such as

useState<number>

Question 4/15

😊 Your answer was correct 🙁 Your answer was incorrect

How can you share state between two React components without passing props explicitly?

const MyContext = React.createContext<{value: string, setValue: React.Dispatch<React.SetStateAction<string>>} | undefined>(undefined);

const MyProvider: React.FC = ({ children }) => {
    const [value, setValue] = useState("");
    return <MyContext.Provider value={{ value, setValue }}>{children}</MyContext.Provider>;
};

const ComponentA: React.FC = () => {
    const context = React.useContext(MyContext);
    return context ? <button onClick={() => context.setValue('Hello')}>Change</button> : null;
};

const ComponentB: React.FC = () => {
    const context = React.useContext(MyContext);
    return context ? <div>{context.value}</div> : null;
};

Available answers

Creating a global object to store state.

Developing a custom hook that returns props.

Utilizing local storage for state persistence.

Using React's Context API to manage shared state.

React's Context API allows components to share data without passing props explicitly through the component tree.

Question 5/15

😊 Your answer was correct 🙁 Your answer was incorrect

In TypeScript, how do you prevent assigning `undefined` to a prop?

interface MyComponentProps {
    name: string;
}

const MyComponent: React.FC<MyComponentProps> = ({ name }) => {
    return <div>Hello, {name}</div>;
};

Available answers

With default parameters in the function implementation.

By initializing the prop with an empty string.

By using `undefined` in the type restriction.

By not using the `?` modifier in the interface declaration.

In TypeScript, to make a parameter non-optional (i.e., prevent it from being

undefined

), you simply omit the

modifier in the type interface definition.

Question 6/15

😊 Your answer was correct 🙁 Your answer was incorrect

How can you ensure a component in TypeScript only accepts props of a specific shape using TypeScript?

interface ButtonProps {
    label: string;
    onClick: () => void;
}

const Button: React.FC<ButtonProps> = ({ label, onClick }) => (
    <button onClick={onClick}>{label}</button>
);

Available answers

Use dynamic prop types with the `any` type.

Use `PropTypes` like in JavaScript React.

Directly declare types in the function body after JSX.

Use an interface to define the prop types and use it in the component type definition.

In TypeScript, interfaces or types are used to explicitly define the shape of props a component accepts, ensuring type safety and auto-completion.

Question 7/15

😊 Your answer was correct 🙁 Your answer was incorrect

Which TypeScript utility can you use to define only some of the properties of an interface as required?

interface Person {
    name: string;
    age: number;
    address?: string;
}

const person: Required<Pick<Person, 'name' | 'age'>> = { name: 'Alice', age: 30 };

Available answers

`Partial` and `Omit` combined.

`Readonly` and `Mutable`.

`Optional` and `Strict`.

`Pick` and `Required` combined.

The

Pick

utility allows you to select a subset of properties, and the

Required

utility enforces the selected properties to be required.

Question 8/15

😊 Your answer was correct 🙁 Your answer was incorrect

In a TypeScript React component, how can you specify that a prop is optional?

interface MyComponentProps {
    name?: string;
}

const MyComponent: React.FC<MyComponentProps> = ({ name }) => {
    return <div>{name}</div>;
};

Available answers

By using an `Optional` type alias.

By using `?` after the prop name.

By using `undefined` in the prop type.

By initializing the prop with `null`.

In TypeScript, you can make a prop optional by adding

after the prop name in the interface.

Question 9/15

😊 Your answer was correct 🙁 Your answer was incorrect

Given the following TypeScript code, what type does the `setColor` function accept?

const [color, setColor] = useState<string | null>(null);

Available answers

Either a string or null.

Only null values.

Only numbers.

Only strings.

The

useState<string | null>

type definition indicates that the state variable and the setter can accept both string and null values.

Question 10/15

😊 Your answer was correct 🙁 Your answer was incorrect

How do you define default props in a React component using TypeScript?

interface MyComponentProps {
    name?: string;
}

const MyComponent = ({ name = "Guest" }: MyComponentProps) => {
    return <div>Hello, {name}</div>;
};

Available answers

Directly in the JSX return statement.

Using `MyComponent.defaultProps`.

Using `static defaultProps` in a class component.

Using default parameter syntax in the props destructuring.

In TypeScript, you can set default values for props by using default parameter syntax during destructuring of the props argument.

Question 11/15

😊 Your answer was correct 🙁 Your answer was incorrect

How can you extend interfaces in TypeScript when creating a React component?

interface BaseProps {
    id: string;
}

interface AdvancedProps extends BaseProps {
    date: Date;
}

const Component: React.FC<AdvancedProps> = ({ id, date }) => (
    <div>{id}: {date.toISOString()}</div>
);

Available answers

By creating a utility type.

By using `implements` keyword.

By merging objects in the component.

By using the `extends` keyword.

In TypeScript, interfaces can be extended using the

extends

keyword, which allows one interface to inherit and augment another.

Question 12/15

😊 Your answer was correct 🙁 Your answer was incorrect

What is the purpose of the `React.FC` type in a TypeScript React component?

const MyComponent: React.FC = () => {
    return <div>Hello, World!</div>;
};

Available answers

To type the props of a functional component.

To declare state in a functional component.

To handle side effects in a component.

To define a class component.

React.FC

is a type alias provided by React for defining function components with props in TypeScript.

Question 13/15

😊 Your answer was correct 🙁 Your answer was incorrect

What is the `key` prop used for in React lists?

const items = ['a', 'b', 'c'];

const listItems = items.map((item, index) => (
    <li key={index}>{item}</li>
));

Available answers

To set a unique id for each HTML element.

To disable an item in a list.

To help React identify which items have changed in a list for efficient re-rendering.

To create a reference pointer for each element.

The

key

prop is crucial for React's list rendering because it helps React identify which items have changed, added, or removed, improving the efficiency of the re-rendering process.

Question 14/15

😊 Your answer was correct 🙁 Your answer was incorrect

How can you indicate that a functional component should only render after certain props are confirmed to be non-null and non-undefined?

const MyComponent: React.FC<{ title?: string }> = ({ title }) => {
    if (!title) {
        return null;
    }
    return <div>{title}</div>;
};

Available answers

By enforcing non-null types at the TypeScript configuration level.

Through custom exception handling in JSX.

By checking the props directly and conditionally rendering a component.

By declaring prop types as `nonNullable` in TypeScript.

You should perform condition checks in the component render logic to determine whether to return content or

null

Question 15/15

😊 Your answer was correct 🙁 Your answer was incorrect

How do you define a prop that accepts children in TypeScript with React?

interface MyComponentProps {
    children?: React.ReactNode;
}

const MyComponent: React.FC<MyComponentProps> = ({ children }) => {
    return <div>{children}</div>;
};

Available answers

By defining the prop type as `Element`.

By defining the prop type as `ReactElement`.

By defining the prop type as `React.ReactNode`.

By defining the prop type as `JSX.Element`.

In React with TypeScript, the

React.ReactNode

type is used to type the

children

prop, as it represents anything that can be rendered in a React component.