A lot of new ways of making functions were introduced in recent versions of Javascript.  Many of them aren't well handled by the console in DevTools.

var baseClass = class {};
var x = [
  function (a = function(){}, b = 1, c = []) {},  // Default arguments
  class abc {  constructor(a, b, c){}  },         // class with constructor
  class def extends baseClass {},                 // class extension,
  class ghi extends function(){} {}               // weird extension
]

When logging x and expanding its properties in the console, the function with default arguments gets cutoff, the constructor's arguments aren't detected, and keywords like extends aren't highlighted in any way.