Use named export for largest series product

.eslintignore

@@ -9,7 +9,6 @@ food-chain
 forth
 grade-school
 grains
-largest-series-product
 linked-list
 list-ops
 meetup

exercises/largest-series-product/example.js

@@ -1,49 +1,26 @@
-export default class Series {
-  constructor(numberString) {
-    if (numberString.match('[^0-9]')) {
-      throw new Error('Invalid input.');
-    }
+const getDigits = numberString => [...numberString].map(digit => parseInt(digit, 10));
 
-    this.numberString = numberString;
-    this.digits = this.getDigits();
+const slices = (digits, sliceSize) => {
+  const result = [];
+  for (let i = 0; i < digits.length - sliceSize + 1; i += 1) {
+    result.push(digits.slice(i, i + sliceSize));
   }
+  return result;
+};
 
-  getDigits() {
-    return [...this.numberString].map(digit => parseInt(digit, 10));
+export const largestSeriesProduct = (numberString, size) => {
+  if (numberString.match('[^0-9]')) {
+    throw new Error('Invalid input.');
   }
-
-  largestProduct(size) {
-    if (size < 0) {
-      throw new Error('Invalid input.');
-    }
-
-    let product,
-      max = 0;
-    this.slices(size).forEach((slice) => {
-      product = slice.reduce((a, b) => a * b, 1);
-      if (product > max) {
-        max = product;
-      }
-    });
-    return max;
+  if (size < 0) {
+    throw new Error('Invalid input.');
   }
-
-  slices(sliceSize) {
-    const result = [];
-    let slice = [];
-
-    if (sliceSize > this.digits.length) {
-      throw new Error('Slice size is too big.');
-    }
-
-    for (let i = 0; i < this.digits.length - sliceSize + 1; i++) {
-      for (let j = 0; j < sliceSize; j++) {
-        slice.push(this.digits[i + j]);
-      }
-      result.push(slice);
-      slice = [];
-    }
-
-    return result;
+  if (size > numberString.length) {
+    throw new Error('Slice size is too big.');
   }
-}
+
+  return slices(getDigits(numberString), size).reduce((max, slice) => {
+    const product = slice.reduce((a, b) => a * b, 1);
+    return product > max ? product : max;
+  }, 0);
+};

exercises/largest-series-product/largest-series-product.spec.js

@@ -1,68 +1,68 @@
-import Series from './largest-series-product';
+import { largestSeriesProduct } from './largest-series-product';
 
 describe('Series', () => {
   test('can get the largest product of 2', () => {
-    expect(new Series('0123456789').largestProduct(2)).toBe(72);
+    expect(largestSeriesProduct('0123456789', 2)).toBe(72);
   });
 
   xtest('works for a tiny number', () => {
-    expect(new Series('19').largestProduct(2)).toBe(9);
+    expect(largestSeriesProduct('19', 2)).toBe(9);
   });
 
   xtest('can get the largest product of 3', () => {
-    expect(new Series('1027839564').largestProduct(3)).toBe(270);
+    expect(largestSeriesProduct('1027839564', 3)).toBe(270);
   });
 
   xtest('can get the largest product of a big number', () => {
-    const largeNumber = '73167176531330624919225119674426574742355349194934969835203127745063262395783180169848018694788' +
-      '51843858615607891129494954595017379583319528532088055111254069874715852386305071569329096329522744304355766896648' +
-      '95044524452316173185640309871112172238311362229893423380308135336276614282806444486645238749303589072962904915604' +
-      '40772390713810515859307960866701724271218839987979087922749219016997208880937766572733300105336788122023542180975' +
-      '12545405947522435258490771167055601360483958644670632441572215539753697817977846174064955149290862569321978468622' +
-      '48283972241375657056057490261407972968652414535100474821663704844031998900088952434506585412275886668811642717147' +
-      '99244429282308634656748139191231628245861786645835912456652947654568284891288314260769004224219022671055626321111' +
-      '10937054421750694165896040807198403850962455444362981230987879927244284909188845801561660979191338754992005240636' +
-      '899125607176060588611646710940507754100225698315520005593572972571636269561882670428252483600823257530420752963450';
-    expect(new Series(largeNumber).largestProduct(13)).toBe(23514624000);
+    const largeNumber = '73167176531330624919225119674426574742355349194934969835203127745063262395783180169848018694788'
+      + '51843858615607891129494954595017379583319528532088055111254069874715852386305071569329096329522744304355766896648'
+      + '95044524452316173185640309871112172238311362229893423380308135336276614282806444486645238749303589072962904915604'
+      + '40772390713810515859307960866701724271218839987979087922749219016997208880937766572733300105336788122023542180975'
+      + '12545405947522435258490771167055601360483958644670632441572215539753697817977846174064955149290862569321978468622'
+      + '48283972241375657056057490261407972968652414535100474821663704844031998900088952434506585412275886668811642717147'
+      + '99244429282308634656748139191231628245861786645835912456652947654568284891288314260769004224219022671055626321111'
+      + '10937054421750694165896040807198403850962455444362981230987879927244284909188845801561660979191338754992005240636'
+      + '899125607176060588611646710940507754100225698315520005593572972571636269561882670428252483600823257530420752963450';
+    expect(largestSeriesProduct(largeNumber, 13)).toBe(23514624000);
   });
 
   xtest('returns 0 if all digits are zero', () => {
-    expect(new Series('0000').largestProduct(2)).toBe(0);
+    expect(largestSeriesProduct('0000', 2)).toBe(0);
   });
 
   xtest('returns 0 if all spans contain zero', () => {
-    expect(new Series('99099').largestProduct(3)).toBe(0);
+    expect(largestSeriesProduct('99099', 3)).toBe(0);
   });
 
   xtest('rejects invalid character in input', () => {
     expect(() => {
-      new Series('1234a5').largestProduct('2');
+      largestSeriesProduct('1234a5', '2');
     }).toThrow(new Error('Invalid input.'));
   });
 
   xtest('rejects negative span', () => {
     expect(() => {
-      new Series('12345').largestProduct(-1);
+      largestSeriesProduct('12345', -1);
     }).toThrow(new Error('Invalid input.'));
   });
 
   xtest('returns 1 for empty string and zero slice length', () => {
-    expect(new Series('').largestProduct(0)).toBe(1);
+    expect(largestSeriesProduct('', 0)).toBe(1);
   });
 
   xtest('returns 1 for non-empty string and zero slice length', () => {
-    expect(new Series('123').largestProduct(0)).toBe(1);
+    expect(largestSeriesProduct('123', 0)).toBe(1);
   });
 
   xtest('throws an error for slices bigger than the number', () => {
     expect(() => {
-      new Series('123').largestProduct(4);
+      largestSeriesProduct('123', 4);
     }).toThrow(new Error('Slice size is too big.'));
   });
 
   xtest('throws an error for empty string and non-zero slice length', () => {
     expect(() => {
-      new Series('').largestProduct(1);
+      largestSeriesProduct('', 1);
     }).toThrow(new Error('Slice size is too big.'));
   });
 });