Default props

js-default-props.js

// Default properties are values that will be set only when they are not included in the original object.
// In this example, user2 does not contain quotes. The setDefaults function ensures all objects have quotes set otherwise it will be set to [].
// When calling setDefaults(user2), the return value will include quotes: [].
// When calling setDefaults(user4), because user4 already has quotes, that property will not be modified.

const user2 = {
  id: 200,
  name: 'Vince Noir'
};

const user4 = {
  id: 400,
  name: 'Bollo',
  quotes: ["I've got a bad feeling about this..."]
};

const setDefaults = ({ quotes = [], ...object}) =>
  ({ ...object, quotes });

setDefaults(user2);
// { id: 200, name: 'Vince Noir', quotes: [] }

setDefaults(user4);
// {
//   id: 400,
//   name: 'Bollo',
//   quotes: ["I've got a bad feeling about this..."]
// }

// It can also be written like this if you want the defaults to appear first instead of last:
const setDefaults = ({ ...object}) => ({ quotes: [], ...object });