polyfills of map, forEach, reduce and flatten object and React optimization and react general questions

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Polyfills for map, forEach, reduce and flatten object. React optimization and general questions.

Polyfills are used to provide modern JavaScript features in older browsers.
map() is used to create a new array with the results of calling a provided function on every element in the array.
forEach() is used to execute a provided function once for each array element.
reduce() is used to reduce the array to a single value by executing a provided function for each element.
Flattening an object means converting a nested object into a single-level object.
React optimization involves techniques like memoization, code splitting, and using PureComponent or React.memo.
React general questions may include component lifecycle, state management, and virtual DOM.

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