Pure ways of editing objects and arrays in JavaScript
tl;dr: use speard operator for both arrays and objects for consistent syntax. Alternatives are Obect.assign() and Array.concat()
Objects
Copying objects
const original = { a: 1, b: 2 }
// Object.assign()
const copy1 = Object.assign({}, original)
// Spread operator
const copy2 = { ...original }
extending objects
const original = { a: 1, b: 2 }
const extension = { c: 3 }
// Combine multiple objects with Object.assign()
const extendedCopy1 = Object.assign({}, original, extension)
// Combine multiple objects with Spread operator
const extendedCopy2 = { ...original, ...extension }
Arrays
Copying arrays
// Copy array
const original = [1, 2, 3]
// .slice() with no args
const copy = [1, 2, 3].slice()
extending arrays
const original = [1, 2, 3]
// Array.concat() returns a new array
const extended = original.concat(4)
const moreExtended = original.concat([4, 5])
// Spread operator
const extended2 = [...original, 3, 4]
const moreExtended2 = [...original, ...extended2]
fyi: according to an article, Array.push() is 945x faster than Array.concat()