uncategorizedFill.js

const categories = [
  {id:1, name:"Web Design"},
  {id:2, name:"Web Development"},
  {id:3, name:"Logo Design"}
]

const data = [
  {id:1, title:"Some title", category: "Web Design"},
  {id:1, title:"Some title", category: "Some new"},
  {id:1, title:"Some title", category: "Web Design"},
  {id:1, title:"Some title", category: "Web Design"},
]

const newData = data.map((item) => {
  const status = categories
    .map((_) => _.name)
    .includes(item.category)
  if(status){
    return item
  }
  else{
    const _item = {...item, category: "Uncategorized"}
    return _item
  }
})
console.log(newData)