for...of statement iterates over data that the iterable object defines to be iterated over.

• Includes built-in String, Array, Array-like objects (e.g., arguments or NodeList), TypedArray, Map, Set, and user-defined iterables

• String, Array, TypedArray, Map and Set are iterables (Iterable objects), because each of their prototype objects implements an @@iterator method.
  • Object (or one of the objects up its prototype chain) has a property with a @@iterator key which is available via constant Symbol.iterator
• Works in terms of .iterator() and .next() and use @iterator property

for...in statement iterates over the enumerable properties of an object, in an arbitrary order.

• Built for iterating object properties.
• Should not be used to iterate over an Array where the index order is important.

for await...of statement creates a loop iterating over async iterable objects as well as on sync iterables

• Includs: built-in String, Array, Array-like objects (e.g., arguments or NodeList), TypedArray, Map, Set, and user-defined async/sync iterables

let / const

• let & const are hoisted but not initialised.
  • The lexically declared variables however stay uninitialised.
  • var is hoisted and initialised with undefined.
• ReferenceError exception is thrown when you try to access it.
• Temporal Dead Zone is everything (trying to access variable) before let/const/class statement is evaluated/initialised.

Arrow function

Spread syntax (splat operator)

Promise

async/await (ES2017)

Template Literals