(JavaScript) Execute a function on callback from other function

Question

This is for vanilla JavaScript. I wan't a function to execute as soon as another function has completely finished. Right now I actually have something that works, but I suppose it can be done better:

setTimeout(function () {
  // does things with the variables a, b(array) and c
}, 500);
function happySunshine(some inparameters){
  // calculates and sets variables a, b(array) and c
}

The happySunshine function must unfortunately lay after my setTimeout function in the order, this cannot change.

Now this works because the happySunshine function will have executed and completed it's tasks during the half second that setTimeout is set to wait before executing.

So... I wan't to know. Is there a way to make a function that is first in the order, wait until another function (later in the order) is completely finished before it executes?

Important to note is that these functions cannot be in the same scope.

Why not declaring the function before and calling it from happySunshine()? You can even pass the parameters if you need to. — mligor
– mligor, Commented Apr 10, 2017 at 9:18
The setTimeout() is the way I have solved the problem right now, I actually don't want it. — Robin Cox
– Robin Cox, Commented Apr 10, 2017 at 9:23
@mligor as I wrote, the functions must be in that order. The happySunshine must come after in order. — Robin Cox
– Robin Cox, Commented Apr 10, 2017 at 9:25
That I understand, but your function inside of setTimeout is called after happySunshine. I don't see the difference between calling this function directly from happySunshine, then from setTimeout. you can declare a function like variable: var myFun = function(){ ... code ..} and call it then from happySunshine. Internally that is what JS engine is doing with setTimeout — mligor
– mligor, Commented Apr 10, 2017 at 9:33

guest271314 · Accepted Answer · 2017-04-10 09:26:40Z

1

You can return Promise.resolve() or Promise constructor from happySunshine() with value set to an object having properties and values a, b, c.

function happySunshine(/* some inparameters */){
  // calculates and sets variables a, b(array) and c
  // return new Promise(function(resolve, reject) {
       // do stuff
       // resolve({a:a, b:[], c:c});
  // });
  return Promise.resolve({a:a, b:[], c:c});
}

happySunshine(/* some inparameters */)
.then(function({a, b, c}) {
  // does things with the variables a, b(array) and c
})

answered Apr 10, 2017 at 9:26

guest271314

1

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3 Comments

Robin Cox Over a year ago

This looks interesting but I don't really understand it. Can you explain what it does? Thanks for helping me!

guest271314 Over a year ago

See You're Missing the Point of Promises

Robin Cox Over a year ago

Thanks guest271314

Spharah · Accepted Answer · 2017-04-10 09:19:12Z

0

Have you tried something like this

function initialFunction(){
//Do you magic here
happySunShine(params);
}

Your happySunShine() method should be available globally otherwise this will not work.

answered Apr 10, 2017 at 9:19

Spharah

6557 silver badges19 bronze badges

1 Comment

Robin Cox Over a year ago

Thanks Spharah, but I don't thik this will work because "//Do you magic here" is dependent that happySunShine(params) will be executed before.

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