array-shuffle-fp - npm Package Compare versions

Comparing version 0.3.0 to 0.4.0

package.json

 {
   "name": "array-shuffle-fp",
-  "version": "0.3.0",
+  "version": "0.4.0",
   "description": "Randomize the order of items in an array using FP style",
@@ -5,0 +5,0 @@ "author": "gziolo",

src/__tests__/fp.js

 const {
 	compose,
+	concat,
+	flip,
+	ifElse,
 	init,
@@ -9,2 +12,3 @@ last,
 	nth,
+	prepend,
 	update
@@ -17,2 +21,5 @@ } = require( '../fp' );
 	const toUpperCase = val => val.toUpperCase();
+	const throwError = () => {
+		throw new Error();
+	};
 
@@ -27,2 +34,32 @@ describe( '#compose', () => {
 
+	describe( '#concat', () => {
+		it( 'returns the result of concatenating the given lists', () => {
+			const result = concat( input )( [ 'f' ] );
+
+			expect( result ).toEqual( [ 'a', 'b', 'c', 'd', 'e', 'f' ] );
+		} );
+	} );
+
+	describe( '#flip', () => {
+		it( 'returns a new function with the first two params order reversed', () => {
+			const result = flip( concat )( [ 'f' ] )( input );
+
+			expect( result ).toEqual( [ 'a', 'b', 'c', 'd', 'e', 'f' ] );
+		} );
+	} );
+
+	describe( '#ifElse', () => {
+		it( 'will process the onTrue function when the result of the condition predicate is true', () => {
+			const result = ifElse( list => length( list ) > 0, last, throwError )( input );
+
+			expect( result ).toBe( 'e' );
+		} );
+
+		it( 'will process the onFalse function when the result of the condition predicate is false', () => {
+			const result = ifElse( list => length( list ) > 100, throwError, last )( input );
+
+			expect( result ).toBe( 'e' );
+		} );
+	} );
+
 	describe( '#init', () => {
@@ -100,2 +137,10 @@ it( 'returns all but the last element of the given list', () => {
 
+	describe( '#prepend', () => {
+		it( 'returns a new list with the given element at the front, followed by the contents of the list', () => {
+			const result = prepend( 'z' )( input );
+
+			expect( result ).toEqual( [ 'z', 'a', 'b', 'c', 'd', 'e' ] );
+		} );
+	} );
+
 	describe( '#update', () => {
@@ -102,0 +147,0 @@ it( 'returns a new copy of the list with the element at the provided index replaced with the given value', () => {

src/fp.js

@@ -1,3 +0,16 @@
-const compose = ( f, g ) => val => f( g( val ) );
+const compose = ( f, g ) =>
+	val => f( g( val ) );
 
+const concat = firstList =>
+	secondList => [].concat( firstList, secondList );
+
+const flip = fn =>
+	b =>
+		a => fn( a )( b );
+
+const ifElse = ( condition, onTrue, onFalse ) =>
+	( list ) => condition( list )
+		? onTrue( list )
+		: onFalse( list );
+
 const init = list => list.slice( 0, list.length - 1 );
@@ -9,28 +22,39 @@
 
-const lessThan = limit => val => val < limit;
+const lessThan = limit =>
+	val => val < limit;
 
-const map = fn => list => list.map( fn );
+const map = fn =>
+	list => list.map( fn );
 
-const nth = n => list => list[ n ];
+const nth = n =>
+	list => list[ n ];
 
-const trampoline = fn => ( ...args ) => {
-	let result = fn( ...args );
+const prepend = el => concat( [ el ] );
 
-	while ( typeof result === 'function' ) {
-		result = result();
-	}
+const trampoline = fn =>
+	( ...args ) => {
+		let result = fn( ...args );
 
-	return result;
-};
+		while ( typeof result === 'function' ) {
+			result = result();
+		}
 
-const update = idx => x => list => {
-	const res = [ ...list ];
+		return result;
+	};
 
-	res[ idx ] = x;
+const update = idx =>
+	x =>
+		list => {
+			const result = [ ...list ];
 
-	return res;
-};
+			result[ idx ] = x;
 
+			return result;
+		};
+
 module.exports = {
 	compose,
+	concat,
+	flip,
+	ifElse,
 	init,
@@ -42,4 +66,5 @@ last,
 	nth,
+	prepend,
 	trampoline,
 	update
 };

src/index.js

 const {
 	compose,
+	concat,
+	flip,
+	ifElse,
 	init,
@@ -8,2 +11,3 @@ last,
 	nth,
+	prepend,
 	trampoline,
@@ -16,16 +20,26 @@ update
 
-function arrayShuffle( scratch, result = [] ) {
-	if ( lessThan2Elements( scratch ) ) {
-		return [ ...scratch, ...result ];
+const arrayShuffleImpl = result => ifElse(
+	lessThan2Elements,
+	flip( concat )( result ),
+	( scratch ) => {
+		const pickIndex = pickRandomIndex( scratch );
+		const pick = nth( pickIndex )( scratch );
+		const updatePickWithLast = compose(
+			update( pickIndex ), last
+		)( scratch );
+
+		return () => arrayShuffleImpl(
+			prepend( pick )( result )
+		)(
+			compose(
+				init, updatePickWithLast
+			)( scratch )
+		);
 	}
+);
 
-	const pickIndex = pickRandomIndex( scratch );
-	const updatePickWithLast = update( pickIndex )( last( scratch ) );
+const arrayShuffle = trampoline(
+	arrayShuffleImpl( [] )
+);
 
-	return () => arrayShuffle(
-		compose( init, updatePickWithLast )( scratch ),
-		[ nth( pickIndex )( scratch ), ...result ]
-	);
-}
-
 module.exports = function( input ) {
@@ -40,3 +54,3 @@ if ( ! Array.isArray( input ) ) {
 
-	return trampoline( arrayShuffle )( input );
+	return arrayShuffle( input );
 };

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Improved metrics

Total package byte prevSize

25957

increased by7.43%

Lines of code

255

increased by37.84%

No dependency changes