React 面试题与答案
相关差异对比
问题 36. What would you do if your React application is rendering slowly?
The cause of slow rendering in React is mostly because of the number of re-render operations, which are sometimes unnecessary. There are two main tools provided by React to help users here:
- memo(): This is used to prevent all of the unnecessary re-rendering carried out by the function components.
- PureComponent: This is used to ensure that the unnecessary re-rendering of class components is avoided.
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问题 37. Can you conditionally add attributes to components in React?
Yes, there is a way in which you can add attributes to a React component when certain conditions are met.
React has the ability to omit an attribute if the value passed to it is not true.
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问题 38. Why is props passed to the super() function in React?
Props gets passed onto the super() function if a user wishes to access this.props in the constructor.
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问题 39. What are the predefined prop types present in React?
There are five main predefined prop types in React. They are as follows:
- PropTypes.bool
- PropTypes.func
- PropTypes.node
- PropTypes.number
- PropTypes.string
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问题 40. What is the difference between Virtual DOM and Real DOM?
| Virtual DOM | Real DOM |
| Changes can be made easily | Changes can be expensive |
| Minimal memory wastage | High demand for memory and more wastage |
| JSX element is updated if the element exists | Creates a new DOM every time an element gets updated |
| Cannot update HTML directly | Able to directly manipulate HTML |
| Faster updates | Slow updates |
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