typescript: array.filter(isObject)-CodePudding

I'm trying to do conditional mongodb aggregations:

collection.aggregate([
  {$match: {}},
  flag & {$lookup: {}},
  flag & {$match: {}},
].filter(isObject))

For that to work I need a typesafe isObject function that works with array.filter.

function isString<T>(argument: T | string): argument is string {
  return typeof argument === 'string';
}

function isObject<T>(argument: T | object): argument is object {
    return argument !== null && typeof argument === 'object'
}

// works
const stringArray: string[] = [
    '{match: 1}',
    false,
    null
].filter(isString)

// doesn't work
const objectArray: object[] = [
    {match: 1},
    false,
    null
].filter(isObject)

Playground Link: Provided

For some reason if I provide real objects it doesn't work. But, it starts to work if I do:

// works again
const objectArray: object[] = [
    {match: 1} as object,
    false,
    null
].filter(isObject)

I don't want to do that and also I don't want to do "array.reduce" or "array.flatMap" or my colleagues beat me up for a bad codestyle.

Is there any way to do that nice and clean?

CodePudding user response：

should work

function isObject<T>(argument: T): argument is Exclude<T, null> & object  {
    return argument !== null && typeof argument === 'object';
}