Generate equation number as a span with unique ID

[piszczu4]

I'm building a math website and I'm wondering whether it would be possible to somehow generate the equation in such a way that it is possible to copy its ID to be able to create a link button which when clicked, it would scroll to that specific equation. Is that possible?

[mbourne]

Hello piszczu4

I see you already discovered this discussion about \eqref, which still doesn't seem resolved: #2003

At first, I was going to suggest a post-processing step which added an ID to each <span class="katex"> ... </span> and you could link to those. But if you have many KaTeX expressions on a page and later need to add or remove some of them in the middle of the page, you'd need to update all the links going to all the expressions after the change. It would be a nightmare to maintain.

So why not do the following:

For each expression that you want to link to, add a <span> around it and give it an ID, some thing like:

Here is Euler's formula <span id="euler_formula"> \( e^{i\pi}+1 = 0 \) </span> and now for a display integral: <span id="int_sin">$$ \int \sin (x) dx = -cos(x) + C $$</span>.

Then you can link to those, something like:

Earlier, we saw <a href="#euler_formula">Euler's formula</a> and a random <a href="#int_sin">sin integral</a>.

[piszczu4]

Yeah thank you, that's the solution I'm going to use in my RichText editor,i.e. allow user to add a label (id) to the equation and number it according to its position within the doc. Bigger problem will be referencing equations from another page, because while label of an equation might not change, the page url might change when its generated dynamically from for example book chapter name. I mean if I have a page myPage/geometry/triangles#theorem1, then when changing the chapter title to triangles-and-squares, the href will stop work and lead to non-existing page. I need to think how to make it works even with such a cases.