var a = ['A', 'B', 'C', 'D'];

var slicedArr = a.slice(1, 3);  // slice starts from 1-index to 3-index, but not include 3-index : ['B', 'C']

console.log(a)
// ["A", "B", "C", "D"]         // slice doesn't change the input
console.log(slicedArr)
// ["B", "C"]
var b = 'ABCD'

var slicedStr = b.slice(1, 3);  // slice process the slice as the array

console.log(b)
// "ABCD"
console.log(slicedStr)
// "BC"