Description

Add 3 new objects related functions and 1 new utility type for union types:

hasProperty

Check if the object has the property, similar to the in operator 'key' in obj but unexistent properties are not allowed and it allows intellisense

Usage:

import { hasProperty } from 'utility-types';

if (hasProperty(obj, 'prop')) {
  // `prop` in `obj`
}

hasDefinedProperty

Check if the object has the property and it is not undefined

Usage:

import { hasDefinedProperty } from 'utility-types';

if (hasDefinedProperty(obj, 'prop')) {
  // `prop` in `obj` and `obj.prop` is not `undefined`
}

hasValorizedProperty

Check if the object has the property and it is not undefined and not null

Usage:

import { hasValorizedProperty } from 'utility-types';

if (hasValorizedProperty(obj, 'prop')) {
  // `prop` in `obj` and `obj.prop` is not `undefined` and not `null`
}

PossibleKeys<T>

Similar to $Keys or keyof, but get keys also from union types

Usage:

type Props = { name: string; employeeId: string } | { name: string; guestId: string };
// Expect: "name" | "employeeId" | "guestId"
type PropsKeys1 = PossibleKeys<Props>;
// Expect: "name"
type PropsKeys2 = $Keys<Props>;
// Expect: "name"
type PropsKeys3 = keyof Props;

Related issues:

• Resolve add "has_property" and "has_value" type guards for objects #189

Checklist

• I have read CONTRIBUTING.md
• I have linked all related issues above
• I have rebased my branch

For bugfixes:

• I have added at least one unit test to confirm the bug have been fixed
• I have checked and updated TOC and API Docs when necessary

For new features:

• I have added entry in TOC and API Docs
• I have added a short example in API Docs to demonstrate new usage
• I have added type unit tests with dts-jest