The use of brackets in javascript arrow function declaration

问题

In ES6/ES2015 arrow functions can be declared with or without brackets around the parameter.

ie:

var foo_1 = myVar => {
  return myVar + 1;
}

or:

var foo_2 = (myVar) => {
  return myVar + 2;
}

What I would like to know is: what is the difference (if any)?

回答1:

There is no differences in your example.

You need parentheses if you

• have no parameter: () => ...
• have multiple parameters: (foo, bar) => ...
• use destructuring: ({foo}) => ...
• use default values: (foo = 42) => ...
• have a rest parameter: (...bar) => ...
• have any combination of the above

In other words, whenever you do not have a single identifier-only parameter.

来源：https://stackoverflow.com/questions/37848328/the-use-of-brackets-in-javascript-arrow-function-declaration