I have this userscript for GreaseMonkey. I created a function (A) which calls an other function (B). I want to wait running the A function further and wait for the B function to return. Function B contains a button, so in fact I want A to wait for the button press.

I tried this with the async and await but that didn't work for me show I now tried to use the .then() option. In the then() I created a function (nextI) to increase the i after running function B.

function A(){

    var i = 0

    while (i < 3){

        var data = jsonResponse[i];

        var x = data.x;

        var y = data.y;

        B(x, y).then(

            nextI(i)

        )

    }

)



function B(x, y){

    // do some stuff

    let button = document.getElementById("button");

    button.addEventListener("click", () => {

        console.log("Button clicked.");

        return

   });

}



function nextI(i){

    return i + 1

}

So I want to pause A until script B is done and I clicked the button.

1. Number is passed by value

Thus, giving i to nextI increases a local copy (i.e. the input parameter).

2. B doesn't return Promise

function B(x, y) {

  let button = document.getElementById("button");



  // FIX HERE

  return new Promise(resolve =>

    button.addEventListener("click", () => {

      console.log("Button clicked.");

      resolve('some data')

    })

  )

}

3. Promise#then accepts a function

So, B (nextI (i)) isn't correct, but B(() => nextI (i)).

N. Other issues

There should be other issues there. For example, you're running functions whose return type/value is Promise in a fire&forget way. Take a look at Promise.all or Promise.race.

before using .then(), you first have to return a promise.

function B(x, y){

  return new Promise((resolve, reject) => { 

     // do something here



     let button = document.getElementById("button"); 

     button.addEventListener("click", () => { 

          console.log("Button clicked."); 

          resolve('foo');

     });



  });

}

take a look https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise