JavaScript Promises : Deep nested context with bind(this)

Question

Because I'm using a prototype that has functions calling other functions in the same prototype I have to refer to that method using this

The Problem this Created:

But because of that, I have to preserve a context to use this that has me forming very ugly .bind(this) walls.

Here is a simplified example I made for laughs.

Killmyself.prototype.fireLeMissles = function () {

    return new Promise(function(resolve,reject) {
        this.anotherFunction(param).then(function(result) {

        someList.forEach(function(item) {
          this.fireLeMissles().then(function(anotherResult){
            promiseList.push(anotherResult)
          })
        },this);
        Promise.all(promiseList).then(function(promiseItem){
          childPlacesIds.forEach(function(childPlaceId) {
            //Do Other Stuff
          },this);
        });
      resolve(result);
    }.bind(this).catch(function(err){
      console.log("Yea, life sucks sometimes.")
    }));
  }.bind(this));
}

Killmyself.prototype.another = function(){
   //Other stuff
}

You can see because of calls to functions in the same prototype such as this.anotherFunction(... and this.fireLeMissles(... I had to do deep preservation of context,which now (in my much larger version of this) is making this code hard to work with.

Question:

Is this a "man up and get use to the harder aspects of JavaScript" thing - or do you seasoned developers see simple ways that deep binding like this could have been avoided?

Answer 1

If you are using ES6, you can benefit from arrow functions, which preserve the context.

var counter = function () {
    this.count = 0;
    setInterval( () => { // arrow function
        console.log(this.count++); // context is preserved
    }, 1000)
}
var counter = new counter();

So, your code would become something like:

Killmyself.prototype.fireLeMissles = function() {
    return new Promise((resolve, reject) => {
        this.anotherFunction(param).then(result => {
            someList.forEach(item => {
                this.fireLeMissles().then(anotherResult => {
                    promiseList.push(anotherResult)
                });
            });
            Promise.all(promiseList).then(promiseItem => {
                childPlacesIds.forEach(childPlaceId => {
                    //Do Other Stuff
                });
            });
            resolve(result);
        }).catch(err => {
            console.log("Yea, life sucks sometimes.")
        });
    });
}

For ES5, you can just either use .bind just like the way you did or you can assign this to something else in the function with the desired context, then use that variable inside the inner functions.

Killmyself.prototype.fireLeMissles = function() {
    var self = this; /// use `self` instead of `this` from now on.
    return new Promise(function(resolve, reject) {
        self.anotherFunction(param).then(function(result) {
            someList.forEach(function(item) {
                self.fireLeMissles().then(function(anotherResult) {
                    promiseList.push(anotherResult)
                })
            });
            Promise.all(promiseList).then(function(promiseItem) {
                childPlacesIds.forEach(function(childPlaceId) {
                    //Do Other Stuff
                });
            });
            resolve(result);
        }).catch(function(err) {
            console.log("Yea, life sucks sometimes.")
        });
    });
}

Answer 2

for starters I do not understand you you need a new Promise.. here, like @loganfsmyth said, I would simply use arrow functions and reduce the complexity:

Killmyself.prototype.fireLeMissles = function (param) {

  return this.anotherFunction(param)
  .then(someList => {
    var promiseList = someList.map( item => this.fireLeMissles(item));
    return Promise.all(promiseList);
  }).then(childPlacesIds => {
    childPlacesIds.forEach(childPlacesId = {
      // .... do something;
    });
    // return something.
  }).catch(err => console.log("Yea, life sucks sometimes."));

}

P. S: I am not sure where this param, someList, childPlacesIds is coming from, and assumed that you are initializing that promiseList as empty array.