let str = "harsh"
let strArray = [...str]
//strArray is now [ 'h', 'a', 'r', 's', 'h' ]
let addEmptyArr = strArray + []
// addEmptyArr is now 'h,a,r,s,h'
let addSameArr = strArray + strArray
// addSameArr is now 'h,a,r,s,hh,a,r,s,h'
why array and string merging show this type of behaviour