This is really cool:
...blah... ... blah blah...
Under the hood it works like this:
function writeImage(url, title) { document.write(`
${title}
`); }
And leads to:
...blah... 
My dog
...blah blah...
Whoa, HTML templating? It inserts the stuff directly where the function is called, and it just works? And it's been available in browsers forever? Stop the presses, I gotta rewrite all my static sites
The same approach works for reusing chunks of HTML between pages:
...page content...
when in common.js you have something like this:
... continue reading