Assistance required in grasping the extent of this particular JavaScript variable

Question

Assistance required in grasping the extent of this particular JavaScript variable

While working in a VueJS SPA with javascript, I am attempting to streamline my code by creating a method that passes the Google Maps Places Service a place_id and specified fields for retrieval.

getPlaceDetails (place, fields) {
  this.$refs.mapRef.$mapPromise.then((map) => {
    var placesServices = new window.google.maps.places.PlacesService(map)
    placesServices.getDetails({ placeId: String(place.place_id), fields: fields }, (result, status) => {
      if (status === window.google.maps.places.PlacesServiceStatus.OK) {
        alert(JSON.stringify(result))
        return result
      }
    })
  })
}

The above method is called from within another method:

var place = this.getPlaceDetails(place, ['name', 'geometry', 'place_id'])

The method executes successfully, displaying the desired JSON in the alert, but 'place' comes back as null. I have attempted various approaches such as setting 'vm = this' before defining 'placesServices' and assigning the result to an app level variable like so:

getPlaceDetails (place, fields) {
  this.$refs.mapRef.$mapPromise.then((map) => {
    var vm = this
    var placesServices = new window.google.maps.places.PlacesService(map)
    placesServices.getDetails({ placeId: String(place.place_id), fields: fields }, (result, status) => {
      if (status === window.google.maps.places.PlacesServiceStatus.OK) {
        alert(JSON.stringify(result))
        vm.tempPlace = result
      }
    })
  }).then(function () {
    return this.tempPlace
  })
}

I am struggling to make the method properly return the 'result' object. Any suggestions on how to achieve this?

javascript google-maps vue.js google-maps-api-3 scope

Answer 1

Answer №1

Understanding Promises

A promise is like making a commitment that something will be resolved or rejected in the future. It is particularly useful for executing tasks asynchronously, such as making HTTP calls, where the time taken for completion is uncertain.

Promises can be linked together (chained) so that they are executed sequentially. The .then method plays a key role in this chaining process. By using .then, you specify a function to be executed once the previous promise is fulfilled. This function will receive the output of the preceding promise.

Implementation Example

getPlaceDetails (place, fields) {
    return this.$refs.mapRef.$mapPromise.then((map) => {
        var vm = this;
        var placesServices = new window.google.maps.places.PlacesService(map);
        placesServices.getDetails({ placeId: String(place.place_id), fields: fields }, (result, status) => {
            if (status === window.google.maps.places.PlacesServiceStatus.OK) {
                alert(JSON.stringify(result));
                return result;
            }
        });
    });
}

This method creates a promise that will eventually produce the desired outcome.

To execute this method and handle its result, you need to obtain the promise and define a function to manage it using .then. This function will run once the result is available.

this.getPlaceDetails(...).then((result) => {
    // Process the obtained result
}}

Alternatively, you can utilize the await operator to pause execution until the promise completes: var place = await this.getPlaceDetails(...);

Answer 2

Understanding Promises

A promise is like making a commitment that something will be resolved or rejected in the future. It is particularly useful for executing tasks asynchronously, such as making HTTP calls, where the time taken for completion is uncertain.

Promises can be linked together (chained) so that they are executed sequentially. The .then method plays a key role in this chaining process. By using .then, you specify a function to be executed once the previous promise is fulfilled. This function will receive the output of the preceding promise.

Implementation Example

getPlaceDetails (place, fields) {
    return this.$refs.mapRef.$mapPromise.then((map) => {
        var vm = this;
        var placesServices = new window.google.maps.places.PlacesService(map);
        placesServices.getDetails({ placeId: String(place.place_id), fields: fields }, (result, status) => {
            if (status === window.google.maps.places.PlacesServiceStatus.OK) {
                alert(JSON.stringify(result));
                return result;
            }
        });
    });
}

This method creates a promise that will eventually produce the desired outcome.

To execute this method and handle its result, you need to obtain the promise and define a function to manage it using .then. This function will run once the result is available.

this.getPlaceDetails(...).then((result) => {
    // Process the obtained result
}}

Alternatively, you can utilize the await operator to pause execution until the promise completes: var place = await this.getPlaceDetails(...);

Answer 3

Answer №2

If you're looking to avoid using return to handle data, one alternative approach is to store the JSON in a Vue watched data variable. Here's an example:

    var myVueInstance = new Vue({
      el: '#myElement',
      data: {
        message: 'Hello from Example.com',
        tempData: {} // <- placeholder for asynchronous data
      },
      methods: {
      fetchData (data) {
        // [...your promise code goes here...]
        }).then((response) => {
           this.tempData = JSON.stringify(response)
           // return this.tempData
        })
  // [...the .then function should be an arrow function to access tempData within scope...]

Answer 4

If you're looking to avoid using return to handle data, one alternative approach is to store the JSON in a Vue watched data variable. Here's an example:

    var myVueInstance = new Vue({
      el: '#myElement',
      data: {
        message: 'Hello from Example.com',
        tempData: {} // <- placeholder for asynchronous data
      },
      methods: {
      fetchData (data) {
        // [...your promise code goes here...]
        }).then((response) => {
           this.tempData = JSON.stringify(response)
           // return this.tempData
        })
  // [...the .then function should be an arrow function to access tempData within scope...]

Assistance required in grasping the extent of this particular JavaScript variable

Answer №1

Understanding Promises

Implementation Example

Answer №2

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