Javascript remove object from array using object variable

Question

So I am trying to use arrays and for demonstration purposes I have condensed the code using points as examples. I want to create a point and push it to array and after doing stuff I want to remove the point from the array.

var PointArray = [];
function CreatePoint(X,Y){
    this.x=X;
    this.y=Y;
    PointArray.push(this);
}
function RemovePoint(PointObject){
     //????
}
var xPoint = CreatePoint(10,10);
//do stuff
RemovePoint(xPoint);

I was looking at the ‍Array.prototype manual and PointArray.Splice seems like a the closest but feels messy since it wants indexs. Anyone have a clean way remove objects from array to shove into function RemovePoint?

Slice is how you do it unless you want to use a library.

Dave Newton
– Dave Newton

2018-08-25 03:52:20 +00:00
Commented Aug 25, 2018 at 3:52 — Dave Newton
– Dave Newton, Commented Aug 25, 2018 at 3:52

CertainPerformance · Accepted Answer · 2018-08-25 04:11:03Z

4

To find the index of something in an array, use indexOf:

function RemovePoint(PointObject){
  const index = PointArray.indexOf(PointObject);
  PointArray.splice(index, 1); // remove one item at index "index"
}

But if you're doing something like this, you might consider using a Set instead, which might be more appropriate if you want a collection, but the index of each object doesn't actually matter - then, you could just call PointSet.delete(PointObject);:

const PointSet = new Set();
function CreatePoint(X,Y){
  this.x=X;
  this.y=Y;
  PointSet.add(this);
}
function RemovePoint(PointObject){
  PointSet.delete(PointObject);
}
console.log(PointSet.size);
const xPoint = new CreatePoint(10,10);
console.log(PointSet.size);
RemovePoint(xPoint);
console.log(PointSet.size);

As comment notes, make sure to use new when calling a constructor like CreatePoint.

edited Aug 25, 2018 at 4:11

answered Aug 25, 2018 at 3:54

CertainPerformance

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3 Comments

MoonEater916 Over a year ago

Ah. I didn't realize i could do that. let me go read the doc on it.

CertainPerformance Over a year ago

@MoonEater916 Works just fine for me - see edit. Calling CreatePoint increases the Set's size to 1, and then calling RemovePoint reduces the size to 0.

MoonEater916 Over a year ago

ya doing a test xPoint is undefined because I didn't put "new" in the line "var xPoint = new CreatePoint(10,10);" Works Great! Thanks @MarkMeyer

Puneet · Accepted Answer · 2018-08-25 04:29:02Z

0

Why not use filter to remove elements from PointArray

var PointArray = [];
function CreatePoint(X,Y){
    this.x=X;
    this.y=Y;
    PointArray.push(this);
}
function RemovePoint(PointObject){
  PointArray = PointArray.filter(singlePoint=>!(singlePoint.x==PointObject.x && singlePoint.y==PointObject.y));
}
var xPoint = new CreatePoint(10,10);
var yPoint = new CreatePoint(20,20);
//do stuff
console.log(PointArray);
RemovePoint(xPoint);
console.log(PointArray);

answered Aug 25, 2018 at 4:29

Puneet

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5 Comments

Dave Newton Over a year ago

In your particular example, because they don't want to remove all points with a specific x/y value, they want to remove a specific entry.

Puneet Over a year ago

But even using a set would not allow to keep duplicates. So no two points have same x and y value

Dave Newton Over a year ago

Depends on how equality is defined, but a set isn't necessarily the right approach-we don't know because the full problem isn't defined.

Puneet Over a year ago

For deleting an item from a set that is a collection of points, the only equality check would be x and y. So will be the insertion check.

Dave Newton Over a year ago

With the current object definition, yes, but that would be a bad way to generally represent points, since it's perfectly valid to have distinct points with the same coordinates. But that's orthogonal to the question, which is how to remove a specific array entry, which may or may not be unique-we simply don't know the problem's parameters.

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