Resolved（Default values for parameters and default values for variables） How to understand this function parameter, ({...} = {}) =>

JavaScript
1

why let an object equals to an empty object like this ?

export const addChat = ({
    // cuid is safer than random uuids/v4 GUIDs
    // see usecuid.org
    id = cuid(),
    msg = '',
    user = 'Anonymous',
    timeStamp = Date.now()
  } = {}) => ({
    type: ADD_CHAT,
    payload: { id, msg, user, timeStamp }
  });
2

It’s a default value in case addChat is called without arguments.

3

Thanks

Why the order like that? Put the empty object on the right

It should be:

function (a=5)
function (object={…} )

Or
function ({}={…})

4

That is how default function parameters look, not to mention any normal assignment variable = value

function logValue(obj = {}) {
  console.log(obj);
}

logValue()
// {}

logValue({
  name: 'Jonh Doe'
})
// {name: "Jonh Doe"}
5

Thanks, I’m understand it for right now.

Default values for parameters and default values for variables

// default values for variables
function move({x = 0, y = 0} = {}) { 
  return [x, y];
}
move({x: 3, y: 8}); // [3, 8]
move({x: 3}); // [3, 0]
move({}); // [0, 0]
move(); // [0, 0]

// Default values for parameters
function move({x, y} = { x: 0, y: 0 }) { 
  return [x, y];
}
move({x: 3, y: 8}); // [3, 8]
move({x: 3}); // [3, undefined]
move({}); // [undefined, undefined]
move(); // [0, 0]