JSFiddle - React, Tailwind, and code Playground

JavaScript

var currentList = ['Daniel', 'Lara', 'Horst'];
var newList = ['Mario', 'Lara'];

var toDelete = [];
var toAdd = [];
for(var i=0;i<newList.length;i++){
    console.log(newList[i],currentList.indexOf(newList[i]))
    if(currentList.indexOf(newList[i]) >-1)
        toAdd.push(newList[i])
}

for(var i=0;i<currentList.length;i++){
   console.log(currentList[i],newList.indexOf(currentList[i]))
   if(newList.indexOf(currentList[i]) == -1)
       toDelete.push(currentList[i]);
}

console.log('dele',toDelete);
console.log('add',toAdd);