Implementation of the Specification Pattern for JavaScript and TypeScript.
Build complex filters and rules easily.
- No external dependencies;
- Fully tested;
- Semantic versioning;
- Forks are welcome! See how to contribute.
$ npm i spec-patternimport { Between } from 'spec-pattern'; const rating = new Between( 1, 5 ); console.log( rating.isSatisfiedBy( 3 ) ); // true console.log( rating.isSatisfiedBy( 0 ) ); // falseimport { Between } from 'spec-pattern'; const desiredAgesToAnswerSurvey = new Between( 16, 21 ) .or( new Between( 65, 120 ) ); console.log( desiredAgesToAnswerSurvey.isSatisfiedBy( 18 ) ); // true console.log( desiredAgesToAnswerSurvey.isSatisfiedBy( 70 ) ); // true console.log( desiredAgesToAnswerSurvey.isSatisfiedBy( 5 ) ); // falseimport { Between, In, GreaterThan } from 'spec-pattern'; const someCrazyRule = new Between( 1, 3 ) .or( new Between( 6, 9 ) ) .or( new In( [ 11, 25, 31 ] ) ) .or( new GreaterThan( 50 ) ); console.log( someCrazyRule.isSatisfiedBy( 2 ) ); // true console.log( someCrazyRule.isSatisfiedBy( 7 ) ); // true console.log( someCrazyRule.isSatisfiedBy( 5 ) ); // false console.log( someCrazyRule.isSatisfiedBy( 11 ) ); // true console.log( someCrazyRule.isSatisfiedBy( 50 ) ); // false console.log( someCrazyRule.isSatisfiedBy( 51 ) ); // true // Printable ! console.log( someCrazyRule.toString() ); // (((between (1, 3) or between (6, 9)) or in [11, 25, 31]) or greater than 50)import { StartsWith, Contains } from 'spec-pattern'; const helloWithoutWorld = new StartsWith( 'Hello' ) .andNot( new Contains( 'world' ) ); console.log( helloWithoutWorld.isSatisfiedBy( 'Hello Bob' ) ); // true console.log( helloWithoutWorld.isSatisfiedBy( 'Hello world' ) ); // falseimport { LengthBetween, EqualTo } from 'spec-pattern'; const crazyText = new LengthBetween( 2, 5 ) .andNot( new EqualTo( 'Hello' ) ); console.log( crazyText.isSatisfiedBy( '' ) ); // false console.log( crazyText.isSatisfiedBy( 'Hi' ) ); // true console.log( crazyText.isSatisfiedBy( 'Hello' ) ); // false console.log( crazyText.isSatisfiedBy( 'Howdy' ) ); // true console.log( crazyText.isSatisfiedBy( 'Hello world' ) ); // falseimport { between } from 'spec-pattern'; const rating = between( 1, 5 ); console.log( rating.isSatisfiedBy( 3 ) ); // true console.log( rating.isSatisfiedBy( 0 ) ); // falseimport { between } from 'spec-pattern'; const desiredAgesToAnswerSurvey = between( 16, 21 ) .or( between( 65, 120 ) ); console.log( desiredAgesToAnswerSurvey.isSatisfiedBy( 18 ) ); // true console.log( desiredAgesToAnswerSurvey.isSatisfiedBy( 70 ) ); // true console.log( desiredAgesToAnswerSurvey.isSatisfiedBy( 5 ) ); // falseimport { between, isIn, greaterThan } from 'spec-pattern'; const someCrazyRule = between( 1, 3 ) .or( between( 6, 9 ) ) .or( isIn( [ 11, 25, 31 ] ) ) .or( greaterThan( 50 ) ); console.log( someCrazyRule.isSatisfiedBy( 2 ) ); // true console.log( someCrazyRule.isSatisfiedBy( 7 ) ); // true console.log( someCrazyRule.isSatisfiedBy( 5 ) ); // false console.log( someCrazyRule.isSatisfiedBy( 11 ) ); // true console.log( someCrazyRule.isSatisfiedBy( 50 ) ); // false console.log( someCrazyRule.isSatisfiedBy( 51 ) ); // true // Printable ! console.log( someCrazyRule.toString() ); // (((between (1, 3) or between (6, 9)) or in [11, 25, 31]) or greater than 50)import { startsWith, contains } from 'spec-pattern'; const helloWithoutWorld = startsWith( 'Hello' ) .andNot( contains( 'world' ) ); console.log( helloWithoutWorld.isSatisfiedBy( 'Hello Bob' ) ); // true console.log( helloWithoutWorld.isSatisfiedBy( 'Hello world' ) ); // falseimport { lengthBetween, equalTo } from 'spec-pattern'; const crazyText = lengthBetween( 2, 5 ) .andNot( equalTo( 'Hello' ) ); console.log( crazyText.isSatisfiedBy( '' ) ); // false console.log( crazyText.isSatisfiedBy( 'Hi' ) ); // true console.log( crazyText.isSatisfiedBy( 'Hello' ) ); // false console.log( crazyText.isSatisfiedBy( 'Howdy' ) ); // true console.log( crazyText.isSatisfiedBy( 'Hello world' ) ); // falseThere is a corresponding sugar function for every available class. Sugar functions are always named in camelCase. For instance, sameValueAs() for the class SameValueAs. The only exception is the class In. Since in is a reserved word in JavaScript and thus cannot be a function name, the corresponding sugar is isIn.
SameValueAs( value: any ): equality of values, not of types, not of instancesStrictSameValueAs( value: any ): equality of values and types, not of instancesEqualTo( value: any ): equality of values or instances, with==StrictEqualTo( value: any ): equality of values and types or of instances, with===SameTypeAs( value: any ): equality of typesGreaterThan( value: any )GreaterThanOrEqualTo( value: any )LessThan( value: any )LessThanOrEqualTo( value: any )Between( min: any, max: any )In( values: array ): inside an arrayStartsWith( value: string, ignoreCase: boolean = false ): string starts withEndsWith( value: string, ignoreCase: boolean = false ): string ends withContains( value: string, ignoreCase: boolean = false ): string containsLengthBetween( min: any, max: any ): string length between two valuesEmpty(): string is empty or array is emptyMatches( regex: RegExp ): matches a regular expressionAny( ...specs: Spec ): composite that takes in multipleSpecs and performs an orAll( ...specs: Spec ): composite that takes in multipleSpecs and performs an and
All these classes extend the abstract class Composite, which in turn implements the interface Spec:
export interface Spec< C, T extends C | unknown > { isSatisfiedBy( candidate: C | T ): boolean; and( other: Spec< C, T > ): Spec< C, T >; andNot( other: Spec< C, T > ): Spec< C, T >; or( other: Spec< C, T > ): Spec< C, T >; orNot( other: Spec< C, T > ): Spec< C, T >; xor( other: Spec< C, T > ): Spec< C, T >; xorNot( other: Spec< C, T > ): Spec< C, T >; not(): Spec< C, T >; }Create your own class by extending the abstract class Composite, like in the following example. Of course, you can also extend one of the aforementioned classes or implement the interface Spec (but why reinventing the wheel, right?).
Let's create a class DifferentFrom ...
...in TypeScript:
import { Composite } from 'spec-pattern'; export class DifferentFrom< C, T extends C | unknown > extends Composite< C, T > { constructor( private _value: T ) { super(); } isSatisfiedBy( candidate: C | T ): boolean { return this._value != candidate; } toString(): string { return 'different from ' + this._value; } }...or in JavaScript 6+:
import { Composite } from 'spec-pattern'; class DifferentFrom extends Composite { constructor( value ) { this.value = value; } isSatisfiedBy( candidate ) { return this.value != candidate; } toString() { return 'different from ' + this.value; } }...or in JavaScript 5+:
var Composite = require( 'spec-pattern' ).Composite; function DifferentFrom( value ) { Composite.call( this ); // super() this.value = value; this.isSatisfiedBy = function ( candidate ) { return this.value != candidate; }; this.toString = function() { return 'different from ' + this.value; }; } DifferentFrom.prototype = Object.create( Composite.prototype ); DifferentFrom.prototype.constructor = DifferentFrom;That's it! Just three methods: constructor, isSatisfiedBy, and toString().