使Javascript调用同步

Question

I'm a bit newer to javascript and am having a hard time figuring out how to work the callbacks in some existing code.

Setup: I have a util.js that contains a lot of helper functions like function

getComments(packageId, successCallback, failCallback, userId)

and

function getActionMemo(packageId, versionId, successCallback, failCallback)

that return the results of an ajax call to the successCallback.

What I need to make, and what I'm struggling with, is a function that amasses the data of the helper functions and to make it more fun, I have a specific order I need to call the helper functions in because there are some data dependencies.

I can hack this by basically copying the code out of the helper functions into a new function and chaining the .done from the ajax call, but this seems like horrible practice. Is there a cleaner way?

Thanks, Erin

Answer 1

Looks like promises could be a solution to your problem. Please read https://www.promisejs.org/

Answer 2

You have a list of actions, these actions are stored in an array or into the html I suppose?

Create an index, starting at 0.

Then in your function you add 1 each time you start the function, select the new action and make your ajax call.

I met your scenario once and will detail the method I used if this doesn't help you.

Answer 3

If it helps, I recently took the first release of the Rogue game written for UNIX in C and rewrote it for javascript to work in a browser. I used a technic called continuation to be able to wait for key entry by the user because in javascript the are no interrupts.

So I would have a piece of code like this:

void function f() {

  // ... first part

  ch = getchar();

  // ... second part

}

that would be transformed in

function f() {

  // ... first part

  var ch = getchar(f_cont1);

  return;
  // the execution stops here 

  function f_cont1 () {

    // ... second part
  }
}

the continuation is then stored to be reuse on a keypressed event. With closures everything would be restarted where it stoped.