Improve isEmpty types

[MarlonPassos-git]

Sumary

Looking for the lodash types of isEmpty they are well advanced.

We could work on the value is to improve typing.

it would be great if typing reached this level:

type User = {
  name: string
  age: number
}

const list: User[] = []
if (_.isEmpty(list)) {
  list // list is undefined[]
} else {
  list // list is User[] 
}

const str = ''
if (_.isEmpty(str)) {
  str // str is ''  
} else {
  str // str is string
}

const obj = {} as User

if (_.isEmpty(obj)) {
  obj // obj is {}
} else {
  obj // obj is User
}

related Issue

sodiray/radash#422

[aleclarson]

Type guards can only narrow the type, so User to {} isn't possible (User is a stricter type). Btw, using the {} type is bad practice, because even primitives can be assigned to it (everything is an object in JavaScript after all!). The TypeScript team recommends using object instead.

For arrays, the more accurate type is never[]. If undefined[] was used, the narrowed type in your example would be User[] & undefined[], so list[0] would result in never anyway.

[MarlonPassos-git]

You are right. We can use these types that you mentioned.

[aleclarson]

Addressed in #219