flatMap()

Use flatMap() creates a new array with sub-array elements flattened by specified depth.

example

[[2], [4], [6], [8]].flatMap(val => val/2) // [ 1, 2, 3, 4 ]

syntax

var new_array = arr.flatMap(function callback(currentValue[, index[, array]]) {
 // return element for new_array
}[, thisArg])

Spread Operator for Objects

Using the spread operator during an Object declaration will assign the properties of the referenced Object to the new Object.

Sự khác biệt giữa substr() và substring() chức năng trong JS là gì?