"I look at this ES6 snippet and honestly question how a junior is meant to memorize and understand this level of code," he writes.
This attitude bugs me. A lot. He thinks of junior developers as of someone who will struggle with the behavior of the reduce function. Not only that, he somehow thinks that the second (ES6) snippet is more difficult for a junior developer to understand than the first one (although the only differences are the arrow function and the object spread operator, which is not, by the way, ES6). What level of qualification should junior developers have then, in his opinion? Where do they come from? Does he picture them as untrained self-taught HTML/CSS enthusiasts? Do CS graduates figure anywhere in his picture, or are they not interested in web development?