I'm trying to parse text obtained from the Wikipedia API.

In detail, I'm trying to parse the wikitext of a whole wiki page into separate sections. On wikipedia, sections are divided by titles enclosed by 2-5 equal symbols (e.g. == TITLE ==). So the whole wikitext of a page has a bunch of this, and I was thinking I'd be able to get the content of each section using split() and regex. Here's my naive try:

let wikitext = text; // Obtained from the API
let sectiontitles = [sectiontitle1, sectiontitle2...]; // Obtained from the API
let sectionsPiped = sectiontitles.join('|');
let regex = new RegExp(`\\={2,5}\\s*(${sectionsPiped})\\s*\\={2,5}`, 'g');
console.log(wikitext.split(regex));

This worked, but not the way I expected. Let's say the wikitext has the following contour (replacing \n with actual linebreaks for readability's sake):

== Section 1 ==
SECTION-1-TEXT
=== Section 1.1 ===
SECTION-1.1-TEXT
=== Section 1.2 ===
SECTION-1.2-TEXT

Then the code above returns:

0: ''
1: 'Section 1'
2: 'SECTION-1-TEXT'
3: 'Section 1.1'
4: 'SECTION-1.1-TEXT'
5: 'Section 1.2'
6: 'SECTION-1.2-TEXT'

but I was expecting:

0: ''
1: 'SECTION-1-TEXT'
2: 'SECTION-1.1-TEXT'
3: 'SECTION-1.2-TEXT'

I guess I'm doing something wrong with the (x|y) regex, so I need your help with this.

Note that API:Parsing_wikitext can parse a single section, but not multiple sections (for this reason I'd have to iterate API requests if I try to do this with the API, but I want to avoid this because the code will otherwise be slow). And in the end, I need to get an array of the contents of each section INCLUDING the title headers like so:

0: ''
1: '== Section 1 ==\nSECTION-1-TEXT'
2: '=== Section 1.1 ===\nSECTION-1.1-TEXT'
3: '=== Section 1.2 ===\nSECTION-1.2-TEXT'

I can do this by adding the headers to the second last array above after spliting the whole wikitext, but is there any easier way to do this? Any help would be appreciated.