ts-narrow

$3

- Library basics
- Library methods
- isString

This library is not supposed to be a schema validator, or a object validator,
so it doesn't throw any errors and will always return a boolean result. You should use
this library as a quick helper to narrow from more generic types, to something that you can work with.

For example:

!image

Here you're receiving an unknown object, which you can't work with on typescript.
By the time the program evaluates the 'if' condition as true, constant a type will be narrow, meaning that now you can be sure that constant a is a object and has a prop b of type number.
This program will enter inside 'if' condition only if constant a matches exactly this condition, _and your IDE will respect these types_.

Under the hood, it uses advanced user defined types to bring the best of two worlds: a fast runtime check within a amazing developer experience.

Library methods

$3

Checks if target is an array and it has an element on a specific position.

$3

Checks if target is an array and it has an element on a specific position.
Can be composed to check the type of the element.

$3

Checks if target is an object and it has a specific property.

$3

Checks if target is an object and it has a specific property.
Can be composed to check the type of the property.

$3

Checks if target is an array.

$3

Checks if target is an array.
Can be composed to check the type of all elements.

$3

Checks if target is a typescript enum.

$3

Checks if target is a specific enum.

$3

Checks if target is a value of a specific enum.

$3

Checks if target is a number.

$3

Checks if target is an object.
Please notice that null is a valid javascript object.

$3

Checks if target is one of passed arguments.

$3

Checks if target is all of passed arguments.

$3

Checks if target is a string.

$3

Checks if target is an object and it has all its properties with the same passed type.

$3

Throws if target is null or undefined.
Can receive an optional message or anything that extends Error to customize the message to be throw.

$3

Checks if target is a literal with specific value.

$3

Checks if target is a object with specific shape.
Can be composed to check the type of each property individually by using a NarrowFunc.
It doesn't care about extra properties.

$3

Checks if target is an instance of a class.

$3

Throws if passed condition is not true.
Can receive a optional message or anything that extends Error to customize the message to be throw.

$3

Throws if passed condition is not true.
It also narrows argument to have matched condition type.
Can receive a optional message or anything that extends Error to customize the message to be throw.

$3

Checks if string is one of strings passed in a list.

$3

Checks if target is a boolean.

$3

Throws if target returns false from a NarrowFunc.

$3

Check if target is not null, undefined.