Signal Equality Functions

[jeffwcx]

Can we add some parameters to the signal for comparing signal values? Currently, the default comparison is simply ‘===’. Perhaps we can refer to Angular signals and allow users to define their own equality functions？

[rschristian]

What's the use case?

[jeffwcx]

Such scenarios are quite common. For example:

• I only want a few properties in the state to participate in the update：

  signal({ value: '1', __internal: 'xx' }, { equals: (a, b) => a.value === b.value })

• Sometimes I want to avoid triggering updates for specific values:

  signal(
    { width: 0, height: 0 }, 
     // Do not trigger changes when width or height are zero 
    { equals: ({ width, height }) => !width || !height }
  );

[rschristian]

I don't think they're that common, given the is the first request for it on this repo ;)

Personally, I'd say you're better off with a different data structure that wraps the values you want in signal(), keeping those values you don't want tracked outside of it. As for "avoid triggering updates", IMO, that goes against the very idea of a reactive container.

That said, adding a comparator method to the signal prototype should probably be workable.

[XantreDev]

It's possible to implement signal with comparsion in user land. Maybe I will make an implementation