https://github.com/vilicvane/is-typeof-property

Simple utilities for tuple type narrowing...
https://github.com/vilicvane/is-typeof-property

Last synced: 4 months ago
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Simple utilities for tuple type narrowing...

• Host: GitHub
• URL: https://github.com/vilicvane/is-typeof-property
• Owner: vilicvane
• License: mit
• Created: 2022-04-04T09:31:06.000Z (over 3 years ago)
• Default Branch: main
• Last Pushed: 2023-10-22T19:49:53.000Z (over 1 year ago)
• Last Synced: 2025-03-24T00:54:54.119Z (4 months ago)
• Language: TypeScript
• Size: 62.5 KB
• Stars: 2
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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# isTypeOfProperty(object, key, type)

> Simple utility for `if (typeof object[property]) ...` type narrowing.

TypeScript as of version 4.6 does not support discriminated union based on the type of properties, so the code below does not work as "expected":

```ts

let value!: {x: string; y: 'string'} | {x: number; y: 'number'};

if (typeof value.x === 'string') {

  // Expecting `value.y` to be 'string', but gets 'string' | 'number'.

}

```

With this utility function:

```ts

import isTypeOfProperty from 'is-typeof-property';

if (isTypeOfProperty(value, 'x', 'string')) {

  // Type of `value.y` is now 'string'.

}

```

## Installation

```sh

yarn add is-typeof-property

# or

npm install is-typeof-property

```

## License

MIT License.