@shedevro/assert

Assert

Library provides assertion utility for better and safe coding.

Features:

• Right assertion return types:

  Assert.someFn(value): asserts value is string or Assert.is.someFn(value): value is string etc.

• Assert functions can be chained with operators (is, all, nullOr, not)

• throws WebUtilsAssertionError (extends from Error). Provides right stacktrace (especialy helpfull then coding with Angular to see links to .ts files)

Installation

npm i @shedevro/assert --save

Usage

First you should import the library

import { Assert } from '@shedevro/assert';

---

Custom error messages

Each function can be customized with you own error message.

Error message supports params injecting of assert functions arguments like input or expected values etc.

Most often the order of params matches the function arguments order.

For example:

const someValue = 3;
Assert.greaterThan(someValue, 10, 'This value should be greater than {2}, but got {1}');
// throw error with message 'This value should be greater than 10, but got 3';

---

Functions

Then you can choice needed function.

Operators

Almost all functions can be chained with different operators.

Moreover, you can combine them each other.

• is – modifies assert functions to return true or false as a result
• all – applies an assert function to a provided array
• nullOr – runs assertion only if input value is defined
• not – inverts assertion action

For example:

// is
const someNumber = 10;
if (Assert.is.range(someNumber, 10, 15)) {
  ...
}


// all
class User {
  id: number;
  name: string;
}

const someArray = [new User(), new User];
Assert.all.instanceOf(someArray, User);

// ...futher actions


// nullOr
const someBoolean = null; // or undefined
Assert.nullOr.boolean(someBoolean);
// ...futher actions


// not
const someFunction = () => 123;
Assert.not.throws(someFunction, TypeError);


// combinations
Assert.is.nullOr.not.emptyString('some string');
Assert.not.endsWith('str', 'some suffix');
Assert.nullOr.all.greaterThan([10, 11, 12, 13], 5);
// ...and so on

---

String Assertions

Method	Description
string(value, message?: string)	Ensures that value is a string
emptyString(value, message?: string)	Ensures that value is an empty string
contains(value, subString: string, message?: string)	Ensures that value contains substring
startsWith(value, prefix: string, message?: string)	Ensures that value starts with some prefix
endsWith(value, suffix: string, message?: string)	Ensures that value ends with some suffix
`oneOf(value, values, message?: string	Ensures that value is one of values (string/number array)

Number Assertions

Method	Description
number(value, message?: string)	Ensures that value is a number
natural(value, message?: string)	Ensures that value is a natural number
greaterThan(value, limit: number, message?: string)	Ensures that value is greater than limit
greaterThanOrEqual(value, limit: number, message?: string)	Ensures that value is greater or equal to limit
lessThan(value, limit: number, message?: string)	Ensures that value is less than limit
lessThanOrEqual(value, limit: number, message?: string)	Ensures that value is less or equal to limit
range(value, min: number, max: number, message?: string)	Ensures that value is in range of min and max

Boolean Assertions

Method	Description
boolean(value, message?: string)	Ensures that value is a boolean
true(value, message?: string)	Ensures that value is true
false(value, message?: string)	Ensures that value is false

Object Assertions

Method	Description
object(value, message?: string)	Ensures that value is an object ({}, not Array or null)

Function Assertions

Method	Description
function(value, message?: string)	Ensures that value is a function

Array Assertions

Method	Description
array(value, message?: string)	Ensures that value is an array
arrayLength(value, expectedLength: number, message?: string)	Ensures that array length is equal to number
arrayMinLength(value, limit: number, message?: string)	Ensures that array length is not less than limit
arrayMaxLength(value, limit: number, message?: string)	Ensures that array length is not greater than limit
arrayLengthBetween(value, min: number, max: number, message?: string)	Ensures that array length is inside a min and max

Instance Assertions

Method	Description
instanceOf(value, instanceClass, message?: string)	Ensures that value is an instance of some class
instanceOfAny(value, instanceClasses, message?: string)	Ensures that value is an instance of any class

RexExp Assertions

Method	Description
match(value, regExp: RegExp, message?: string)	Ensures that value is match a regular expression

Other Assertions

Method	Description
defined(value, message?: string)	Ensures that value is defined (not null, undefined or NaN)
equal(value, expect, message?: string)	Ensures that value is equal to expec (value === expect)
throws(expression: () => any, errorClass?, message?: string)	Ensures that expression throws some error

Authors

Shedevro

All credits for great idea to @webmozart with his webmozart/assert for PHP!

Contribute

If you have ideas on how to improve this library, you are welcome!

Please read readme of root project directory.

License

The content of this package is licensed under the MIT license.