如何编写带有参数的同步函数作为异步函数（Javascript）？

Question

Suppose I have the following code:

Synchronous Version:

    var waitingToGetValue = heavyProcessingFunc (para1, para2);
    response.send(waitingToGetValue);

I tried looking around but all I got were functions without parameter.

Asynchronous Attempt:

    heavyProcessingFunc(para1, para2, (function(waitingToGetValue){
       response.send(waitingToGetValue);
    });

I need to send the two parameters to the function. The function returns a value that I need to use to then send it to the response.

Does it even matter if I put it in a asynchronous format? Can anyone recommend me a video/source that easily explains the difference synchronous vs asynchronous: I read many material for the past few days and it just keep getting more confusing with promises, callbacks, and trying to access the values outside those functions.

Answer 1

  function heavyProcessingFunc(para1, para2, callback){ console.log('We have two params to work with', para1, para2); setTimeout(function(){// Simulating a long request callback("Now we send the response by calling the callback"); // This is waitingToGetValue },3000); } heavyProcessingFunc("para1", "para2", function(waitingToGetValue){ console.log(waitingToGetValue); // response.send(waitingToGetValue); });