The Spread Operator is "..." three dots, which allows to extend an object.
Code for adding attributes to an existing json object:
var parts = ['shoulders', 'knees'];
var lyrics = ['head', ...parts, 'and', 'toes']; // ["head", "shoulders", "knees", "and", "toes"]
You can also extend the same object also:
parts = [...parts, 'and', 'toes'];