CODEWITHSUNDEEP
javascript
Jóni
Jóni

Reputation: 374

How to sum properties of two objects in javascript

I'm trying to do something I don't remember/find if it is possible in javascript.

I have an object constructor "Point" and I want to know if it possible to, for example, sum two different objects like bellow.

function Point(x, y) {
    this.x = x;
    this.y = y;
}

a = new Point(1,2);
b = new Point(2,3);
c = a+b;


console.log('a: ', a)
console.log('b: ', b)
console.log('c: ', c)

a = Point {x: 1, y: 2}
b = Point {x: 2, y: 3}
Expected result: c = Point {x: 3, y: 5}

Upvotes: 3

Views: 1826

Answers (5)

Jóni
Jóni

Reputation: 374

So, it turns out that is possible to do it. It just isn't advisable to do it.

I found the solution after some more digging in an old post: Fake operator overloading in JavaScript article and git Fake operator overloading for JavaScript code

credit to Axel Rauschmayer, the author 

function Point(x, y) {
  if (arguments.length === 0) {
    x = 0;
    y = 0;
  } else if (arguments.length !== 2) {
    throw new Error("Need either 0 or 2 arguments");
  }
  this.x = x;
  this.y = y;
}

//-------------- Operator overloading
Point.operands = [];

Point.prototype.valueOf = function() {
  Point.operands.push(this);
  // Lowest natural number x where the following are all different:
  // x + x, x - x, x * x, x / x
  return 3;
}
Object.defineProperty(Point.prototype, "_", {
  set: function(value) {
    var ops = Point.operands;
    var operator;
    if (ops.length >= 2 && (value === 3 * ops.length)) {
      operator = this.setAdd;
    } else {
      throw new Error("Unsupported operation (code " + value + ")");
    }
    Point.operands = []; // reset
    return operator.apply(this, ops);
  },
  get: function() {
    return this.toString();
  }
});

//-------------- Operator implementations
Point.prototype.setAdd = function(first) {
  this.x = first.x;
  this.y = first.y;
  [].slice.call(arguments, 1).forEach(function(op) {
    this.x += op.x;
    this.y += op.y;
  }, this);
  return this;
}

//-------------- Various helpers
Point.prototype.toString = function() {
  return "Point(" + this.x + ", " + this.y + ")";
}
Point.prototype.equals = function(other) {
  return this.x === other.x && this.y === other.y;
}

//-------------- Testing it
var p = new Point();
var a = new Point(1, 2);
var b = new Point(4, 3);

p._ = a + b;
console.log(p); // Point {x: 5, y: 5}

Upvotes: 1

Gyumeijie
Gyumeijie

Reputation: 172

You may not simply use the + operator. In javascript an object will be converted to primitive(string or number) if it is in an AdditiveExpression.

So there is not a clean way to sum properties of two objects in javascript, you may need to create an additional function.

Upvotes: 0

Suresh
Suresh

Reputation: 923

function sumOfObjects(Obj1, Obj2){
    var finalObj = {};
    this.keys(Obj1).forEach(value =>{
        if (Obj2.hasOwnProperty(value)) {
            finalObj[value] = Obj1[value] + Obj2[value]
        }  
    });
    return finalObj;
 }

Upvotes: 4

Raghav Garg
Raghav Garg

Reputation: 3707

You can do something like below code. We are adding a static method on Point function which will add two objects and return new object.

function Point(x, y) {
    this.x = x;
    this.y = y;
}

Point.add = function(a, b) {
    const x = a.x + b.x;
    const y = a.y + b.y;
    return new Point(x, y)
}

a = new Point(1,2);
b = new Point(2,3);
c = Point.add(a, b)


console.log('a: ', a)
console.log('b: ', b)
console.log('c: ', c)

Upvotes: 1

Jojo Narte
Jojo Narte

Reputation: 3104

You can create a function for this. A function that should accept the two points should be enough, then in the implementation create a new Point that contains the sum of each property.

function addPoint(pointA, pointB) {
 const newX = pointA.x + pointB.x;
 const newY = pointA.y + pointB.y;
 return new Point(newX, newY);
}

This is the most basic code you can do for it, but for instance there are other approaches such as allowing multiple parameters then generating the sum for all of it would require a different approach as well.

Upvotes: 2

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