Functions that perform HTTP requests are not considered pure because they have side effects. Purity in functions means that they do not cause any observable side effects, and HTTP requests involve external actions that can impact the program's state.

In JavaScript, when you declare a constant variable (const) inside a block (like an if statement or a loop), the scope of that variable is limited to the block. This means it cannot be accessed outside of that block.

Tree shaking can be leveraged by importing only the necessary components from the third-party library. This way, the bundler can exclude the unused parts during the build process, optimizing the bundle size. The other options are not efficient for tree shaking purposes.

The reduce method is used to execute a reducer function on each element of the array, resulting in a single output value.

Dynamic imports are especially useful for asynchronous loading of modules. Unlike traditional synchronous imports, dynamic imports allow modules to be loaded asynchronously, enabling the application to continue executing code without waiting for the module to be fully loaded. This asynchronous behavior is beneficial for optimizing performance, especially in scenarios where certain modules are only needed under specific conditions. Understanding the advantages of asynchronous module loading is crucial for developing efficient and responsive JavaScript applications.

The correct option is Properties. When using mixins in ES6, there can be conflicts between the properties of the mixin and the target class. It's important to handle these conflicts appropriately to ensure the correct behavior of the composed object.

When a generator function is called, it returns an iterator object. This object can be used to iterate through the values generated by the generator using the next() method. The other options do not represent the initial return type of a generator function.

ES6 supports dynamic property names through computed property names. By using square brackets around an expression within an object literal, you can create properties with names determined at runtime. This enhances the flexibility and expressiveness of object literals.

In-depth content in the explanation. ES6 introduces the concept of tail call optimization, allowing for deeper recursion without causing a stack overflow. Tail calls occur when a function's last action is a recursive call, and ES6 optimizes these tail calls to prevent excessive stack usage.

Unlike objects, where keys are converted to strings, a Map in JavaScript can have keys of any data type. So, the correct answer is string.