Q741. How do you create an array with some data?
You can create an array with some data or an array with the same values using `fill` method. ```javascript var newArray = new Array(5).fill("0"); console.log(newArray); /...
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Q742. What are error boundaries in React v16?
**Note:** Error boundaries were introduced in React 16 and remain valid in current React versions (18/19). _Error boundaries_ are components that catch JavaScript errors ...
Q743. What are the placeholders from console object?
Below are the list of placeholders available from console object, 1. %o — It takes an object, 2. %s — It takes a string, 3. %d — It is used for a decimal or integer These...
Q744. How are error boundaries handled in React v15?
**⚠️ LEGACY:** This question is only relevant for historical context. React v15 is extremely outdated (released in 2016). React v15 provided very basic support for _error...
Q745. Is it possible to add CSS to console messages?
Yes, you can apply CSS styles to console messages similar to html text on the web page. ```javascript console.log( "%c The text has blue color, with large font and red ba...
Q746. What is the purpose of render method of `react-dom`?
This method is used to render a React element into the DOM in the supplied container and return a reference to the component. If the React element was previously rendered...
Q747. What is the purpose of dir method of console object?
The `console.dir()` is used to display an interactive list of the properties of the specified JavaScript object as JSON. ```javascript const user = { name: "John", id: 1,...
Q748. What will happen if you use `setState()` in constructor?
When you use `setState()`, then apart from assigning to the object state React also re-renders the component and all its children. You would get error like this: _Can onl...
Q749. Is it possible to debug HTML elements in console?
Yes, it is possible to get and debug HTML elements in the console just like inspecting elements. ```javascript const element = document.getElementsByTagName("body")[0]; c...
Q750. Is it good to use `setState()` in `componentWillMount()` method?
**⚠️ DEPRECATED:** `componentWillMount()` has been removed in React 17+. This question is only relevant for legacy React applications. **Historical Context:** While it wa...