Type Guards TS

type-guards-ts is a TypeScript library providing a collection of type guard functions to help you perform runtime type checking and type narrowing. This library includes functions to check if a value is of a certain type (e.g., isBoolean) as well as functions to check if a value is not of a certain type (e.g., isNotBoolean).

Index

- Installation
- How to Use
- Available Type Guards
- How to Use Each Type Guard
- isBigInt
- isBoolean
- isFunction
- isNull
- isNumber
- isObject
- isString
- isSymbol
- isUndefined
- isArray
- isDate
- isNotBigInt
- isNotBoolean
- isNotFunction
- isNotNull
- isNotNumber
- isNotObject
- isNotString
- isNotSymbol
- isNotUndefined
- isNotArray
- isNotDate
- Future Releases

Installation

To install the package, run the following command:

``bash
npm install type-guards-ts
`

How to Use

To use the type guards provided by type-guards-ts, you can import the required functions from the package and use them in your TypeScript code. Here’s a quick example:

`typescript
import { isBoolean } from "type-guards-ts";

const value: unknown = true;

if (isBoolean(value)) {
// TypeScript now knows that value is a boolean
console.log("The value is a boolean.");
} else {
console.log("The value is not a boolean.");
}
`

Available Type Guards

- isBigInt
- isBoolean
- isFunction
- isNull
- isNumber
- isObject
- isString
- isSymbol
- isUndefined
- isArray
- isDate
- isNotBigInt
- isNotBoolean
- isNotFunction
- isNotNull
- isNotNumber
- isNotObject
- isNotString
- isNotSymbol
- isNotUndefined
- isNotArray
- isNotDate

How to Use Each Type Guard

$3

Checks if a value is a BigInt.

`typescript
import { isBigInt } from "type-guards-ts";

const value: unknown = BigInt(123);

if (isBigInt(value)) {
console.log("The value is a BigInt.");
} else {
console.log("The value is not a BigInt.");
}
`

$3

Checks if a value is a boolean.

`typescript
import { isBoolean } from "type-guards-ts";

const value: unknown = true;

if (isBoolean(value)) {
console.log("The value is a boolean.");
} else {
console.log("The value is not a boolean.");
}
`

$3

Checks if a value is a function.

`typescript
import { isFunction } from "type-guards-ts";

const value: unknown = () => {};

if (isFunction(value)) {
console.log("The value is a function.");
} else {
console.log("The value is not a function.");
}
`

$3

Checks if a value is null.

`typescript
import { isNull } from "type-guards-ts";

const value: unknown = null;

if (isNull(value)) {
console.log("The value is null.");
} else {
console.log("The value is not null.");
}
`

$3

Checks if a value is a number.

`typescript
import { isNumber } from "type-guards-ts";

const value: unknown = 42;

if (isNumber(value)) {
console.log("The value is a number.");
} else {
console.log("The value is not a number.");
}
`

$3

Checks if a value is an object.

`typescript
import { isObject } from "type-guards-ts";

const value: unknown = { key: "value" };

if (isObject(value)) {
console.log("The value is an object.");
} else {
console.log("The value is not an object.");
}
`

$3

Checks if a value is a string.

`typescript
import { isString } from "type-guards-ts";

const value: unknown = "Hello, world!";

if (isString(value)) {
console.log("The value is a string.");
} else {
console.log("The value is not a string.");
}
`

$3

Checks if a value is a symbol.

`typescript
import { isSymbol } from "type-guards-ts";

const value: unknown = Symbol("symbol");

if (isSymbol(value)) {
console.log("The value is a symbol.");
} else {
console.log("The value is not a symbol.");
}
`

$3

Checks if a value is undefined.

`typescript
import { isUndefined } from "type-guards-ts";

const value: unknown = undefined;

if (isUndefined(value)) {
console.log("The value is undefined.");
} else {
console.log("The value is not undefined.");
}
`

$3

Checks if a value is an array.

`typescript
import { isArray } from "type-guards-ts";

const value: unknown = [];

if (isArray(value)) {
console.log("The value is an array.");
} else {
console.log("The value is not array.");
}
`

Below is an example of documentation in Markdown format that teaches how to use the isDate and isNotDate type guards.

---

$3

Description:
Checks whether the provided value is a Date object.
This function verifies if the given value is a Date by first checking whether it is an instance of Date. It also uses Object.prototype.toString to handle cases where the Date object might come from a different execution context.

Usage Example:

`typescript
import { isDate } from "type-guards-ts";

const value: unknown = new Date();

if (isDate(value)) {
console.log("The value is a Date:", value);
} else {
console.log("The value is not a Date.");
}
`

$3

Checks if a value is not a BigInt.

`typescript
import { isNotBigInt } from "type-guards-ts";

const value: unknown = 123;

if (isNotBigInt(value)) {
console.log("The value is not a BigInt.");
} else {
console.log("The value is unknown.");
}
`

$3

Checks if a value is not a boolean.

`typescript
import { isNotBoolean } from "type-guards-ts";

const value: unknown = "true";

if (isNotBoolean(value)) {
console.log("The value is not a boolean.");
} else {
console.log("The value is unknown.");
}
`

$3

Checks if a value is not a function.

`typescript
import { isNotFunction } from "type-guards-ts";

const value: unknown = "function";

if (isNotFunction(value)) {
console.log("The value is not a function.");
} else {
console.log("The value is unknown.");
}
`

$3

Checks if a value is not null.

`typescript
import { isNotNull } from "type-guards-ts";

const value: unknown = "not null";

if (isNotNull(value)) {
console.log("The value is not null.");
} else {
console.log("The value is unknown.");
}
`

$3

Checks if a value is not a number.

`typescript
import { isNotNumber } from "type-guards-ts";

const value: unknown = "42";

if (isNotNumber(value)) {
console.log("The value is not a number.");
} else {
console.log("The value is unknown.");
}
`

$3

Checks if a value is not an object.

`typescript
import { isNotObject } from "type-guards-ts";

const value: unknown = "object";

if (isNotObject(value)) {
console.log("The value is not an object.");
} else {
console.log("The value is unknown.");
}
`

$3

Checks if a value is not a string.

`typescript
import { isNotString } from "type-guards-ts";

const value: unknown = 123;

if (isNotString(value)) {
console.log("The value is not a string.");
} else {
console.log("The value is unknown.");
}
`

$3

Checks if a value is not a symbol.

`typescript
import { isNotSymbol } from "type-guards-ts";

const value: unknown = "symbol";

if (isNotSymbol(value)) {
console.log("The value is not a symbol.");
} else {
console.log("The value is unknown.");
}
`

$3

Checks if a value is not undefined.

`typescript
import { isNotUndefined } from "type-guards-ts";

const value: unknown = "defined";

if (isNotUndefined(value)) {
console.log("The value is not undefined.");
} else {
console.log("The value is unknown.");
}
`

$3

Checks if a value is not an array.

`typescript
import { isNotArray } from "type-guards-ts";

const value: unknown = "not array";

if (isNotArray(value)) {
console.log("The value is not an array.");
} else {
console.log("The value is not unknown.");
}
`

$3

Description:
Determines if the provided value is not a Date object.
This type guard leverages the isDate helper function to check if a value is not a Date. If the value is not a Date, the function returns true and narrows the type accordingly.

Usage Example:

`typescript
import { isNotDate } from "type-guards-ts";

const value: unknown = "2023-08-24"; // Example value that is not a Date

if (isNotDate(value)) {
console.log("The value is not a Date:", value);
} else {
console.log("The value is a Date.");
}
`

Future Releases

Currently, this package focuses on type guards for primitive types. However, we're actively working on expanding the library to include type guards for non-primitive types. Stay tuned for future releases where you'll find new and enhanced functionalities!

Keep your code safe and type-safe with type-guards-ts`! 🚀