I'm trying to implement a vector object instantiated like below...

var a = new Vector([1,2,3]);
var b = new Vector ([2,2,2]);

...and when I do a math operation I need something like this...

a.add(b); // should return Vector([3,4,5])

...but my code below returns me just an array

function Vector(ponents) {
  // TODO: Finish the Vector class.
  this.arr = ponents;
  this.add = add;
}

function add(aa) {
  if(this.arr.length === aa.arr.length) {
    var result=[];
    for(var i=0; i<this.arr.length; i++) {
       result.push(this.arr[i]+aa.arr[i]);
    }
    return result;
  } else {
    return error;
  }
}

Please help me out here. Thank you!

I'm trying to implement a vector object instantiated like below...

var a = new Vector([1,2,3]);
var b = new Vector ([2,2,2]);

...and when I do a math operation I need something like this...

a.add(b); // should return Vector([3,4,5])

...but my code below returns me just an array

function Vector(ponents) {
  // TODO: Finish the Vector class.
  this.arr = ponents;
  this.add = add;
}

function add(aa) {
  if(this.arr.length === aa.arr.length) {
    var result=[];
    for(var i=0; i<this.arr.length; i++) {
       result.push(this.arr[i]+aa.arr[i]);
    }
    return result;
  } else {
    return error;
  }
}

Please help me out here. Thank you!

• javascript
• arrays
• vector

• Why not move to a functional approach to manipulate Vectors ? This meduim article explains the advantages very well. hackernoon./… – dorriz Commented Apr 10, 2019 at 13:07

3 Answers 3

Perhaps it is simpler to extend javascript's native Array, so that there is no need for keeping around an extra Vector.arr property. Here is a simple implementation called for learning purposes that boils down to this, in modern JS:

class Vector extends Array {
  // example methods
  add(other) {
    return this.map((e, i) => e + other[i]);
  }
}

// example usage
let v = new Vector(1, 2, 3);
console.log(v.add(v));

This class inherits Array's constructor. Note passing in a single value creates an empty Array of that length and not a length 1 Array. Vector would require a super call in the constructor to inherit exotic Array behavior, such as having a special length property, but this shouldn't be needed for a math vector of fixed length. You can include fancier constructor behavior here, such as being able to construct from an Array as input.

You need to wrap up your resulting array in a new Vector object:

function Vector(ponents) {
  // TODO: Finish the Vector class.
  this.arr = ponents;
  this.add = add;
}

function add(aa) {
  if(this.arr.length === aa.arr.length) {
    var result=[];
    for(var i=0; i<this.arr.length; i++) {
       result.push(this.arr[i]+aa.arr[i]);
    }
    return new Vector(result);
  } else {
    return error;
  }
}

I should note also that you may want to do further reading on creating JavaScript objects, in the area of creating methods (such as your add method) on the prototype of the Vector object. There are many good tutorials out there.

The solution by James looks good but it's a bit old-fashioned in my opinion. Here is a way to solve the problem in modern ES6 Javascript Classes.

class Vector {
  constructor(arr) {
    this.arr = arr;
  }
  add(otherVector) {
    const oa = otherVector.arr;
    if (this.arr.length === oa.length) {
      let res = []
      for(let key in this.arr) {
        res[key] = this.arr[key] + oa[key]
      }
      return new Vector(res)
    }
  }
}