Q2261. What is the output of below spread operator array?
```javascript [..."John Resig"]; ``` The output of the array is ['J', 'o', 'h', 'n', ' ', 'R', 'e', 's', 'i', 'g'] **Explanation:** The string is an iterable type and the...
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Q2262. What is the difference between HOCs and Hooks?
Both **Higher-Order Components (HOCs)** and **Hooks** let you reuse logic across components, but they solve that problem in very different ways. | Aspect | Higher-Order C...
Q2263. How is set() implemented internally? I've seen people say that set objects in Python have O(1) membership-checking. How are they implemented internally to allow this? What sort of data structure does it use? What other implications does that implementation have?
Indeed, CPython's sets are implemented as something like dictionaries with dummy values (the keys being the members of the set), with some optimization(s) that exploit th...
Q2264. Is PostMessage secure?
Yes, postMessages can be considered very secure as long as the programmer/developer is careful about checking the origin and source of an arriving message. But if you try...
Q2265. Does `React.memo` prevent Context consumers from re-rendering?
**No.** `React.memo` only performs a shallow comparison of a component's **props** — it has no visibility into context. If a component reads a value via `useContext`/`Con...
Q2266. What is MRO in Python? How does it work?
Method Resolution Order (MRO) it denotes the way a programming language resolves a method or attribute. Python supports classes inheriting from other classes. The class b...
Q2267. What are the problems with postmessage target origin as wildcard?
The second argument of postMessage method specifies which origin is allowed to receive the message. If you use the wildcard “\*” as an argument then any origin is allowed...
Q2268. How would you create a reusable Context?
A **reusable Context** bundles the `createContext` call, its `Provider` (with local state/logic), and a custom hook to consume it into a single module. This hides the raw...
Q2269. What is the difference between old style and new style classes in Python?
Declaration-wise: New-style classes inherit from object, or from another new-style class. ```python class NewStyleClass(object): pass ``` class AnotherNewStyleClass(NewSt...
Q2270. How do you avoid receiving postMessages from attackers?
Since the listener listens for any message, an attacker can trick the application by sending a message from the attacker’s origin, which gives an impression that the rece...