Deleting or moving an object from an array of objects

Authoring Twine
1

Using Sugarcube 2.30

<<set $objArray1 to { “test1”: { somekey: 1 }, “test2”: { somekey: 1} }>>
<<set $objArray2 to { “test3”: { somekey: 3} }>>

I understand I can use jQuery.extend to add objArray2 to objArray1

All works well.

How do I remove/delete a specific object like “test2”? Better yet, how do I move “test2” object into another object array like objArray3?

2

Object arrays aren’t really arrays. They’re just an object with a bunch of members. You can index over an objects members like an array, but it’s not really one.

For example:

// this object
var bleh = new function() {
    this.a = 1;
    this.b = 2;
};

// is the same as
var bleh = {a: 1, b: 2};

That having been said, it’s actually a lot easier to delete items and move items from an object than an array.

// initialize 
var test1 = {a: 1, b: 1};
var test2 = {};

// copy
test2.a = test1.a;
// another way of writing it
test2["a"] = test1["a"];

// delete
delete test1.a;
// or
delete test1["a"];

Edit: Revised answer to use delete operator.

3

Wow. That worked just as I needed. Thank you!

4

I had a brainfart and forgot that delete existed. Both methods work, but setting it to undefined will leave the member but with a value of undefined.

Two takeaways from this is that in both instances if (test1.a === undefined) will return true. Also, I believe the item will not be saved to local storage in both cases. Undefined items get removed when converting to JSON.

However, an example of the differences:

var test = {a: 1, b: 2};

test.a = undefined; // test = {a: undefined, b: 2}
delete test.a; // test = {b: 2};

Hopefully that all makes sense.

5

@sirslice

The TwineScript equivalent of the above JavaScript code would look like…

<<run delete test1.a >>
or
<<run delete test1["a"] >>

note: You could also use the <<set>> macro in place of the above <<run>> macro calls, because the two macros are functionally identical. I use the <<run>> macro because I feel it reads better when doing actions like this.

1 Like
6

Just got back on to ask that very question. Thanks!

7

If it helps, you might also want to check out the “Arrays vs Generic Objects” section of the UInv help file. It goes over different ways of working with the two.