async/await 是异步的还是同步的？

Question

I'm actually diving into the asyc/await part for the first time so I am having a hard time understanding it.

I know that async await is used to make a function run in an async manner but how, because as per the definition, the "await" keyword halts the execution of a function until the promise is resolved, and then executes the leftover code in the function. Isn't this a synchronous behaviour, because things are getting executed in order as they should be?

Feel free to help me out of my confusion or if I am wrong somewhere.

Answer 1

Neither.

The async and await keywords are tools to manage promises .

Promises are a tool to manage asynchronous code .

If you mark a function as async then:

• its normal return value is replaced with a promise that resolves to its normal return value.
• you may use await inside it

If you use await on the left hand side of a promise, then the containing function will go to sleep until the promise settles. Execution outside the async function will continue while it sleeps (ie is is not halted ).

This lets you use syntax that looks like it works on synchronous code to work on asynchronous code.

It doesn't make synchronous operations asynchronous or vice versa.