Spread Operator

SpreadOperator.js

/*
* Array spread operator
*/
const arr = [1, 3, 5]

arr.concat(7)
// [1, 3, 5, 7] // returns a new array, doesn't change arr

arr.push(11)
// [1, 3, 5, 11] // actually changes arr

console.log(...arr)
// 1, 3, 5, 11

console.log([...arr, 13, 42])
// [ 1, 3, 5, 11, 13, 42 ]

console.log(arr)
// [1, 3, 5, 11]

/*
* Object spread operator
* * Must install "transform-object-rest-spread" as a babel plugin
*/
const obj = {
  name: 'Person',
  age: 55
}

console.log({ id: 123, ...obj, location : 'Jeddah' })
// {
//  id: 123,
//  name: "Person",
//  age: 55,
//  location: "Jeddah"
// }

console.log({ age: 44, ...obj }) // Will NOT override 'age'
// {age: 55, name: "Person"}

console.log({ ...obj, age: 44 }) // WILL override 'age'
// {name: "Person", age: 44}