What is the easiest way to implement html include?

Question

HTML

Greetings, I need the ability to include pieces of code from one file to another without using a template engine or using some kind of html-allowing syntax. Maybe use post-processing? I used to use jade, but here the project does not allow this

Answer 1

gulp-rigger
The insertion itself happens like this
//= template/header.html

Answer 2

SSI
HTML Import - Include for the Web: Part 2

Answer 3

includeHTML - can load parts of HTML markup either via an HTML tag or as a function. Asynchronously, synchronously, call-back support, correct recursive loading of all nested parts.