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spec-pattern

Implementation of theSpecification Pattern for JavaScript and TypeScript.

Build complex filters and rules easily.

No external dependencies;
Fullytested;
Semantic versioning;
Forks are welcome! Seehow to contribute.

Installation

$ npm i spec-pattern

Usage

Without syntax sugar

A simple Between rule

import{Between}from'spec-pattern';constrating=newBetween(1,5);console.log(rating.isSatisfiedBy(3));// trueconsole.log(rating.isSatisfiedBy(0));// false

A little more complex Between rule

import{Between}from'spec-pattern';constdesiredAgesToAnswerSurvey=newBetween(16,21).or(newBetween(65,120));console.log(desiredAgesToAnswerSurvey.isSatisfiedBy(18));// trueconsole.log(desiredAgesToAnswerSurvey.isSatisfiedBy(70));// trueconsole.log(desiredAgesToAnswerSurvey.isSatisfiedBy(5));// false

Composing rules

import{Between,In,GreaterThan}from'spec-pattern';constsomeCrazyRule=newBetween(1,3).or(newBetween(6,9)).or(newIn([11,25,31])).or(newGreaterThan(50));console.log(someCrazyRule.isSatisfiedBy(2));// trueconsole.log(someCrazyRule.isSatisfiedBy(7));// trueconsole.log(someCrazyRule.isSatisfiedBy(5));// falseconsole.log(someCrazyRule.isSatisfiedBy(11));// trueconsole.log(someCrazyRule.isSatisfiedBy(50));// falseconsole.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)

Not only numbers

import{StartsWith,Contains}from'spec-pattern';consthelloWithoutWorld=newStartsWith('Hello').andNot(newContains('world'));console.log(helloWithoutWorld.isSatisfiedBy('Hello Bob'));// trueconsole.log(helloWithoutWorld.isSatisfiedBy('Hello world'));// false

import{LengthBetween,EqualTo}from'spec-pattern';constcrazyText=newLengthBetween(2,5).andNot(newEqualTo('Hello'));console.log(crazyText.isSatisfiedBy(''));// falseconsole.log(crazyText.isSatisfiedBy('Hi'));// trueconsole.log(crazyText.isSatisfiedBy('Hello'));// falseconsole.log(crazyText.isSatisfiedBy('Howdy'));// trueconsole.log(crazyText.isSatisfiedBy('Hello world'));// false

With syntax sugar

A simple Between rule

import{between}from'spec-pattern';constrating=between(1,5);console.log(rating.isSatisfiedBy(3));// trueconsole.log(rating.isSatisfiedBy(0));// false

A little more complex Between rule

import{between}from'spec-pattern';constdesiredAgesToAnswerSurvey=between(16,21).or(between(65,120));console.log(desiredAgesToAnswerSurvey.isSatisfiedBy(18));// trueconsole.log(desiredAgesToAnswerSurvey.isSatisfiedBy(70));// trueconsole.log(desiredAgesToAnswerSurvey.isSatisfiedBy(5));// false

Composing rules

import{between,isIn,greaterThan}from'spec-pattern';constsomeCrazyRule=between(1,3).or(between(6,9)).or(isIn([11,25,31])).or(greaterThan(50));console.log(someCrazyRule.isSatisfiedBy(2));// trueconsole.log(someCrazyRule.isSatisfiedBy(7));// trueconsole.log(someCrazyRule.isSatisfiedBy(5));// falseconsole.log(someCrazyRule.isSatisfiedBy(11));// trueconsole.log(someCrazyRule.isSatisfiedBy(50));// falseconsole.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)

Not only numbers

import{startsWith,contains}from'spec-pattern';consthelloWithoutWorld=startsWith('Hello').andNot(contains('world'));console.log(helloWithoutWorld.isSatisfiedBy('Hello Bob'));// trueconsole.log(helloWithoutWorld.isSatisfiedBy('Hello world'));// false

import{lengthBetween,equalTo}from'spec-pattern';constcrazyText=lengthBetween(2,5).andNot(equalTo('Hello'));console.log(crazyText.isSatisfiedBy(''));// falseconsole.log(crazyText.isSatisfiedBy('Hi'));// trueconsole.log(crazyText.isSatisfiedBy('Hello'));// falseconsole.log(crazyText.isSatisfiedBy('Howdy'));// trueconsole.log(crazyText.isSatisfiedBy('Hello world'));// false

Available sugar

There is a corresponding sugar function for every available class. Sugar functions are always named incamelCase.For instance,sameValueAs() for the classSameValueAs.The only exception is the classIn. Sincein is a reserved word in JavaScript and thus cannot be a function name, the corresponding sugar isisIn.

Available classes

SameValueAs( value: any ): equality of values, not of types, not of instances
StrictSameValueAs( value: any ): equality of values and types, not of instances
EqualTo( 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 types
GreaterThan( value: any )
GreaterThanOrEqualTo( value: any )
LessThan( value: any )
LessThanOrEqualTo( value: any )
Between( min: any, max: any )
In( values: array ): inside an array
StartsWith( value: string, ignoreCase: boolean = false ): string starts with
EndsWith( value: string, ignoreCase: boolean = false ): string ends with
Contains( value: string, ignoreCase: boolean = false ): string contains
LengthBetween( min: any, max: any ): string length between two values
Empty(): string is empty or array is empty
Matches( regex: RegExp ): matches a regular expression
Any( ...specs: Spec ): composite that takes in multipleSpecs and performs an or
All( ...specs: Spec ): composite that takes in multipleSpecs and performs an and

All these classes extend the abstract classComposite, which in turn implements the interfaceSpec:

exportinterfaceSpec<C,TextendsC|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>;}

Creating your own class

Create your own class by extending theabstract classComposite, like in the following example. Of course, you can also extend one of the aforementioned classes or implement the interfaceSpec(but why reinventing the wheel, right?).

Let's create a classDifferentFrom ...

...in TypeScript:

import{Composite}from'spec-pattern';exportclassDifferentFrom<C,TextendsC|unknown>extendsComposite<C,T>{constructor(private_value:T){super();}isSatisfiedBy(candidate:C|T):boolean{returnthis._value!=candidate;}toString():string{return'different from '+this._value;}}

...or in JavaScript 6+:

import{Composite}from'spec-pattern';classDifferentFromextendsComposite{constructor(value){this.value=value;}isSatisfiedBy(candidate){returnthis.value!=candidate;}toString(){return'different from '+this.value;}}

...or in JavaScript 5+:

varComposite=require('spec-pattern').Composite;functionDifferentFrom(value){Composite.call(this);// super()this.value=value;this.isSatisfiedBy=function(candidate){returnthis.value!=candidate;};this.toString=function(){return'different from '+this.value;};}DifferentFrom.prototype=Object.create(Composite.prototype);DifferentFrom.prototype.constructor=DifferentFrom;