Assertion API

The assertThat API is the cornerstone of string validation in Regist. It offers a fluent and chainable interface for making assertions about your strings, allowing you to verify everything from email formats to password strength with ease.

Getting Started

To begin using the assertThat API, import the assertThat function from the regist library. Pass the string you want to validate to this function, and then chain the desired assertion methods.

import { assertThat } from 'regist';
 
// Example: Check if a string is a valid email address
const isValidEmail = assertThat('test@example.com').isEmail().try(); // Returns true
 
// Example: Validate a strong password
const isStrong = assertThat('Password123!').isStrongPassword().try(); // Returns true

Chaining Assertions

The power of the assertThat API lies in its ability to chain multiple assertions together. This enables you to build complex and precise validation rules in a readable and maintainable way.

import { assertThat } from 'regist';
 
// Example: Validate a username
const isValidUsername = assertThat('testuser')
  .isAlphaNumeric()
  .lengthIs({ min: 3, max: 20 })
  .try(); // Returns true

API Reference

Below is a comprehensive list of the assertion methods available in the assertThat API.

Method	Description
`.has(str)`	Checks if the string contains a specific substring.
`.doesNotHave(str)`	Checks if the string does NOT contain a specific substring.
`.startsWith(str)`	Checks if the string starts with a specific substring.
`.endsWith(str)`	Checks if the string ends with a specific substring.
`.isExactly(str)`	Checks for an exact match to the provided string.
`.isNot()`	Negates the next assertion in the chain.
`.isAlpha()`	Checks if all characters in the string are letters.
`.isAlphaNumeric()`	Checks if all characters are letters or digits.
`.hasAllUppercase()`	Checks if all letters in the string are uppercase.
`.hasAllLowercase()`	Checks if all letters in the string are lowercase.
`.isUpperCase()`	Checks if the string contains at least one uppercase letter.
`.isLowerCase()`	Checks if the string contains at least one lowercase letter.
`.isDigit()`	Checks if all characters in the string are digits.
`.isNumeric()`	Checks if the string can be converted to a number.
`.isWhitespace()`	Checks if all characters are whitespace.
`.isEmail()`	Checks if the string is a valid email address.
`.isUrl()`	Checks if the string is a valid URL.
`.isUrlSafe()`	Checks if the string contains only URL-safe characters.
`.isPhone(preset)`	Checks for a valid phone number based on a country preset (e.g., 'US', 'UG').
`.isNumberConvertible()`	Checks if the string can be safely converted to a number.
`.passesRegex(regex)`	Checks if the string matches a custom regex pattern.
`.failsRegex(regex)`	Checks if the string does NOT match a custom regex pattern.
`.anyOf(...values)`	Checks if the string is equal to any of the provided values.
`.lengthIs(n \| {min,max})`	Checks if the string's length is a specific number or within a range.
`.isBetween(start, end)`	Checks if a substring exists between two markers.
`.hasNoEmoji()`	Checks if the string contains no emoji.
`.anagram(str)`	Checks if the string is an anagram of the provided string.
`.isPalindrome()`	Checks if the string is a palindrome.
`.hasUniqueCharacters()`	Checks if all characters in the string are unique.
`.whereValueAt(idx).is(val)`	Checks if the character at a specific index matches a value.
`.wordCount()`	Checks the number of words in the string.
`.isBase64()`	Checks if the string is a valid base64 string.
`.isStrongPassword()`	Checks for strong password criteria (min 8 chars, upper, lower, digit, special char).
`.customCheck(fn)`	Applies a custom predicate function for validation.
`.stringTransform()`	Switches to the `stringTransform` API with the current string value.
`.try(handler?)`	Executes the assertion chain, returning `true` or `false`. If a handler is provided, it's called on error.

👾 Regist

Assertion API

Getting Started

Chaining Assertions

API Reference

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