了解JavaScript中的异步/等待模式(Understanding Async/Await patterns in JavaScript)

 我对JavaScript编程比较陌生，所以回调函数一直给我带来麻烦。 我使用的是一个支持ES7（Meteor）的“async / await”语法的框架，但是我很难理解如何实现一个调用其他函数的异步函数。 
 
 
 
 我想要做的事：用户输入一个URL，从URL中提取数据，处理并放入数据库。 我希望这是以非阻塞的方式进行的，以便用户可以在发生此过程时继续使用该应用程序。 
 
 
 伪代码： 
 
async function foo(URL) {
    try {
        //using request-promise npm package to make the request
        const data = await makeRequestPromise(URL) 
        const parsedData = await myParsingFunciton(data);
        MyDB.insert({
            parsedData,
        });
    catch (err) {
        console.log(err);
    }
 
 所以我有几个问题： 
 
 
 
 在这个异步函数的非阻塞范围内发生了什么？ 
 
 
 如果是这样，我可以只使用一系列同步函数，因为在我收到数据之前我无法解析数据？ 
 
 
 如果我尝试等待未定义为异步的函数（例如myParsingFunction），会发生什么情况？ 我的研究似乎暗示该功能被迫返回一个承诺，但我不确定如何确定。 在代码中这样做并不会返回错误，但JavaScript在回报方面似乎令人惊讶地容忍古怪。 
 
 
 我想补充一点，我的函数可以工作，而且事情进入数据库，但我不知道如何测试它是否实际上是非阻塞的。 

I'm relatively new to JavaScript programming, and so callbacks have been giving me trouble. I'm using a framework that supports the "async/await" syntax from ES7 (Meteor), but I'm having some difficulty understanding exactly how I can implement an asynchronous function that calls other functions.
 
 
 
What I want to do: The user enters a URL, data is fetched from the URL, processed, and put into a database. I want this to occur in a non-blocking manner, so that the user can continue to use the application while this process is occurring.
 
 
Pseudocode:
 
async function foo(URL) {
    try {
        //using request-promise npm package to make the request
        const data = await makeRequestPromise(URL) 
        const parsedData = await myParsingFunciton(data);
        MyDB.insert({
            parsedData,
        });
    catch (err) {
        console.log(err);
    }
 
So I have a few questions:
 
 
 
Is anything that happens in the scope of this async function non-blocking?
 
 
If so, can I just use a series of synchornous functions since I can't parse the data before I receive it anyway?
 
 
What happens if I try to await a function that is not defined as asynchronous (for example myParsingFunction)? My research seems to imply that the function is forced to return a promise, but I'm not certain how I would determine that. Doing so in the code does not return an error, but JavaScript seems surprisingly tolerant of weirdness with regards to returns.
 
 
I would like to add that my function works and things go into the database, but I have no idea how to test if it is actually non-blocking. 

原文：https://stackoverflow.com/questions/42677043