async, await and Promises 

JavaScript adding Promises greatly improved the use of callbacks, because callbacks can now be defined after calling the function instead of before. This allows the code to be cause then effect, rather than reversed as with callback functions.

await and async are boilerplate saving language constructs.

An async function always returns a Promise, but the function is written as if it returns the Promise resolve value. It also enables the use of await inside the function.

Putting await in front of calling a function that returns a Promise automatically waits for the Promise to resolve, and provides the resolving value.

These future language features can be used in current environments, such as NodeJS or web browsers, through the use of a transpiler, such as Babel.
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