Question

Javascript Noob calling for duty!

I would like to write the code for the following:

var p1 = new LatLon(userLat, userLon);                                                    
var p2 = new LatLon(destLat, destLon);  
var dist = p1.distanceTo(p2);    

which means I need to create a Javascript struct of sorts that will create a position and then also be able to take a second position as an argument. I DO NOT need the code to calculate the distance. I just need to figure out how to create the object and allow it to accept the arguments. Here is my pseudo code/ failed attempt:

function LatLon(userLat, userLon) {
    var pos = {
      'lat': userLat, 'lon': userLon, 'distanceTo': distanceBetweenTwoPos(pos, pos2);
    }
    return pos;
}

function distanceBetweenTwoPos(pos, pos2){
    // here I will do my own calculations. 
}

Any help on getting something similar to the above, yet functional?

Answer 1

Using the typical prototypal inheritance approach, it could look like this.

function LatLon(userLat, userLon) {
    this.lat = userLat;
    this.lon = userLon;
}

LatLon.prototype.distanceTo = function(pos2){
    console.log(this.lat, pos2.lat);
    console.log(this.lon, pos2.lon);
    // return the result
}

Inside the LatLon constructor, because you’re calling it with new, this is a reference to the object being constructed, return statement is needed; it’ll return the new object.

Inside distanceTo, this will be a reference to the object that called the method, so in your code, it would be a reference to the p1 object.

And of course p2 will be passed as an argument.

var p1 = new LatLon(userLat, userLon);
var p2 = new LatLon(destLat, destLon);  
var dist = p1.distanceTo(p2);