What is the behavior of uncaught errors in React 16?
- They are ignored
- They are logged to the console
- They trigger a fatal error and crash the application
- They trigger an error boundary to catch the error
Uncaught errors in React 16 and later versions trigger a fatal error and crash the application. This behavior was introduced in order to prevent subtle bugs and inconsistencies that could result from errors being silently ignored or logged to the console.
What is Concurrent Rendering?
- A rendering technique for low-end devices
- A rendering technique for high-end devices
- A new feature in React 18
- A way to render multiple parts of a component tree at the same time
Concurrent Rendering is a new rendering strategy introduced in React 18 that allows multiple parts of a component tree to be rendered at the same time, without blocking the UI thread. This means that the user interface can remain responsive while React is rendering updates. Concurrent Rendering is particularly useful for large and complex applications that need to maintain high performance.
How to pass a parameter to an event handler or callback?
- Using an arrow function
- Using the bind method
- Using the event object
- Using the setState method
A parameter can be passed to an event handler or callback in React by using an arrow function. The arrow function takes the event as a parameter, along with any additional parameters that need to be passed. This approach ensures that the event object is properly handled and that the correct parameters are passed to the event handler or callback.
How to update a component every second?
- Use the setInterval() function in the componentDidMount() method
- Use the setInterval() function in the constructor method
- Use the setTimeout() function in the componentDidUpdate() method
- Use the setTimeout() function in the render() method
In React, you can update a component every second by using the "setInterval()" function in the "componentDidMount()" lifecycle method. This will create a timer that updates the component state every second, causing the component to re-render with the new state values. For example: componentDidMount() { this.timerID = setInterval(() => this.tick(), 1000); }.
How to reset state in Redux?
- Dispatch a RESET action
- Modify the state directly
- Use the combineReducers function
To reset the state in Redux, you can dispatch a RESET action to the Redux store. This action can be handled by a reducer function that returns the initial state of the application. This allows you to reset the application state to its initial values.
Is it keys should be globally unique?
- Yes, always
- No, never
- It depends on the use case
In React, keys should be globally unique whenever possible. This helps React identify which items have changed, added, or removed from a list, and update the UI accordingly. While keys do not have to be globally unique in all cases, it is generally a best practice to use unique keys whenever possible.
Why do we use array destructuring (square brackets notation) in useState?
- It's a personal preference of the developer
- It's required by the React API
- It's a cleaner way to write the code
- It allows us to name the state variables
When using useState in React, the function returns an array with two elements: the state value and a function to update the state value. By using array destructuring (square brackets notation), we can name the state variables to make our code more readable and easier to maintain.
What is the recommended way for naming components?
- Use a long name that includes the component's functionality
- Use a name that is the same as the component's file name
- Use a name that is the same as the component's parent folder
- Use a simple name that describes the component
The recommended way for naming components in React is to use a simple name that describes the component. The name should be a noun or noun phrase that accurately represents the component's purpose. This makes it easier to understand and maintain the code, as well as to reuse the component in other parts of the application.
How do you access props in attribute quotes?
- {props}
- {someProp}
- {this.props.someProp}
- {this.props}
In React, you can access props in attribute quotes by using the "this.props" syntax and the name of the prop. For example, to access a prop named "someProp", you would use the syntax "{this.props.someProp}" inside the attribute quotes. This allows you to dynamically set attributes based on props, such as setting the value of an input field or the source of an image.
What is the purpose of push and replace methods of history?
- To add or replace a new route to the history stack
- To clear the history stack and start a new session
- To navigate to the previous route in the history stack
- To update the current route without adding a new entry to the history stack
The push and replace methods of the history object are used to add or replace a new route to the history stack. The push method adds a new entry to the history stack and navigates to the specified route, while the replace method updates the current entry in the history stack without adding a new one. These methods are commonly used for programmatic navigation and managing the browser history in React applications.