arrow function、function.apply

An arrow function expression has a shorter syntax than a function expression and does not have its own this, arguments, super, or new.target. These function expressions are best suited for non-method functions, and they cannot be used as constructors.

Syntax

Basic Syntax

(param1, param2, …, paramN) => { statements }
(param1, param2, …, paramN) => expression
// equivalent to: => { return expression; } 

// Parentheses are optional when there's only one parameter name:
(singleParam) => { statements }
singleParam => { statements }

// The parameter list for a function with no parameters should be written with a pair of parentheses.
() => { statements }

function.apply

The apply() method calls a function with a given this value, and arguments provided as an array (or an array-like object).

Note: While the syntax of this function is almost identical to that of call(), the fundamental difference is that call() accepts an argument list, while apply() accepts a single array of arguments.

Syntax

function.apply(thisArg, [argsArray])