React.js, often simply called React, is a highly popular JavaScript library for building user interfaces. Developed and maintained by Facebook, React is renowned for its component-based architecture and the ability to efficiently update and render components when data changes. It is a foundational tool for developing modern web and mobile applications, allowing developers to create dynamic and interactive user interfaces with ease. React's vast ecosystem, including tools like React Native for mobile app development, makes it a top choice for frontend development and a key player in the world of web technologies.
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Practice Test
71. In React, what is the primary purpose of a form element?
A. Displaying text
B. Accepting user input
C. Styling web pages
D. Managing server-side data
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Answer: Accepting user input
72. In React, how do you handle user input in controlled components?
A. By using the onChange event
B. By using the onClick event
C. By using the onSubmit event
D. By using the onMouseOver event
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Answer: By using the onChange event
73. Which React event is commonly used to handle changes in an input field's value?
A. onClick
B. onMouseOver
C. onChange
D. onSubmit
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Answer: onChange
74. What is the purpose of the value prop in a React input element?
A. To display placeholder text
B. To set the initial input value
C. To trigger form submission
D. To change the component's state
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Answer: To set the initial input value
75. In React, what is the recommended way to handle form submission?
A. Using the onClick event
B. Using the onSubmit event
C. Using the onChange event
D. Using the onMouseOver event
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Answer: Using the onSubmit event
76. What is the primary benefit of controlled components in React forms?
A. Simplicity and ease of use
B. Improved form performance
C. Enhanced security
D. Server-side data management
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Answer: Simplicity and ease of use
77. In React, what does the defaultValue prop do when used with an input element?
A. It sets the initial input value
B. It triggers an event when the input changes
C. It prevents user input
D. It displays placeholder text
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Answer: It sets the initial input value
78. Which React library is commonly used for form validation in React applications?
A. React Formik
B. React Router
C. React Redux
D. React Axios
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Answer: React Formik
79. In a React form, how do you prevent the default form submission behavior when handling form submission?
A. By using the e.preventDefault() method
B. By using the form.preventDefault() method
C. By using the form.preventSubmit() method
D. By using the e.preventFormSubmit() method
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Answer: By using the e.preventDefault() method
80. What is the purpose of the required attribute in a React input element?
A. To set the input value as required
B. To validate the input on submission
C. To disable user input
D. To hide the input field
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Answer: To validate the input on submission
