o add elements to an array at a specific index in JavaScript, you would typically use the splice() method. The splice() method allows you to specify the index where you want to add elements and the number of elements to remove (if any). This method can be used for both adding and removing elements at a specific position in an array. For example, myArray.splice(2, 0, 'newElement') would add 'newElement' at index 2 of myArray.

The for...in loop is primarily used for iterating over the properties of an object, not for arrays. It helps access each property name (key) of an object. Attempting to use it with arrays can lead to unexpected results, as it may also iterate over non-index properties added to the array.

Brendan Eich is credited as the main developer behind JavaScript's creation. He created JavaScript while working at Netscape Communications in 1995. His contributions to the language's design and development have had a lasting impact on web development.

The common problem addressed by using asynchronous code in JavaScript is the avoidance of blocking the main thread. Blocking the main thread can lead to unresponsive user interfaces, making the application seem slow or frozen. Asynchronous code helps prevent this issue by allowing non-blocking execution of tasks.

To manage successive data retrieval operations in a clean and maintainable manner, you can use the "Async/Await" approach in JavaScript. Async/Await simplifies asynchronous code and makes it look more like synchronous code, which can significantly enhance code readability and maintainability. It allows you to write asynchronous code in a more sequential style, making it easier to handle multiple asynchronous operations.

CORS (Cross-Origin Resource Sharing) is the API that allows you to make non-simple requests (such as those with custom headers or methods) to another domain in JavaScript while considering the Same-Origin Policy. XMLHttpRequest is an older alternative but has limitations compared to CORS. JSONP is a workaround technique, not an API, and WebSocket is used for full-duplex communication, not for cross-origin requests.

JavaScript's major shift into server-side programming was largely enabled by Node.js. Node.js is a runtime environment that allows JavaScript to be executed on the server, making it suitable for building scalable, server-side applications. It revolutionized web development by unifying front-end and back-end languages.

For...of loops are preferred when working with asynchronous code because they automatically handle Promise resolution. When you iterate over an iterable that contains Promises, for...of will await each Promise and provide the resolved value, making it more convenient for working with asynchronous operations.

The primary difference is that in a while loop, the condition is checked before executing the code block. If the condition is initially false, the code block may never run. In contrast, the do-while loop guarantees that the code block is executed at least once because it checks the condition after executing the block. This makes do-while useful when you want the code to run once before checking the condition.

The Equality (===) operator can be used to compare both value and type in JavaScript. It checks if two values are strictly equal, meaning they have the same value and the same data type. The other options, such as Assignment (=) and Identity (==), do not perform strict value and type comparison. Inequality (!=) checks for inequality.