How to properly use array.map and other ES stuff in TypeScript?

Question

typescript

I started to learn TypeScript and rewrite existing code to it, but there was a problem when using the array.map() method. Do I need to pass the interface of the object to it, or is it enough to define only the object at the output?
It turned out without errors to do so, but something tells me that I'm on the wrong path)

.map((item: any) => {
  let countItems: number = item.name.toLocaleLowerCase().indexOf(search.toLocaleLowerCase()) !== -1 ? 1 : 0
  let newItem: ItemInterface = {
    ...item,
    countItems: countItems
  }
  return newItem;
})
.filter((item: any) => {
  return item.countItems > 0 || item.name.toLocaleLowerCase().indexOf(search.toLocaleLowerCase()) !== -1
})

Answer 1

In this case, all types are inferred automatically. They do not need to be specified.

[].map(item => ({
    ...item,
    countItems: item.name.toLocaleLowerCase().indexOf(search.toLocaleLowerCase()) !== -1 ? 1 : 0
  }))
.filter(item=>item.countItems > 0 || item.name.toLocaleLowerCase().indexOf(search.toLocaleLowerCase()) !== -1)