Fat arrow is well understood in the JS community because of CoffeeScript, and that is one reason why people are pushing for fat arrow to be accepted. I personally think CoffeeScripts has had a very large impact on the idea.
These kinds of changes have been floating around for javascript since long before coffeescript.
currently, function(){} is the exact same as the proposed ()->{}, and (function(){}).bind(this) is the exact same as ()=>{}
>"Fat arrow functions do not have prototype properties, which makes them cheaper to make. They are immutable."
One of the first ideas with CoffeeScript was to simplify function syntax, mostly because JavaScript's anonymous functions are so useful and pervasive that you end up with a lot of this:
_.each(toRemove, function(key){ delete data[key]; });
Arrows were appealing for a shorthand function syntax because of their visual representation of what happens in a (pure) function. Input goes in one side, output comes out the other. The input determines, or points to, the output. Since we use parentheses symmetrically to group parameters to a function, both when you define a function and when you call one, we arrive at this:
(input) -> output
_.each toRemove, (key) -> delete data[key]