What causes IOS to have a JS regex issue?

Question

JavaScript

Goodness, I ran into a problem that IOS devices do not understand JS regular expressions, not all, but only one, but very important for the project. Because of the regular expression, the execution of the script stops. the problem is that IOS does not understand or something else "?<=" and "?<", when I remove them it works, but the meaning of the search changes. Tell me where to look and how it is solved? Thanks in advance
let reg = /(?<=<tag>)([\s\S]*?)(?=<\/tag>)/g;

Answer 1

https://caniuse.com/#feat=js-regexp-lookbehind