String template builder

string_template_builder.js

function reverse(...a){
  let res = '';
  const templates = Array.isArray(a) && a.length > 0 ? a[0]:null;
  if(templates){
    for(let i = 0; i < templates.length; i++) {
      const placeholder = a[i+1];
      res+=templates[i];
      if(placeholder) res+=`${placeholder} :: ${placeholder.split('').reverse().join('')}`
    }
  }
  return res;
}

reverse`Reverse this_ ${'Hello'}
And this -> ${'World!'}
And this ^^ ${'Hello World!'}`;