Solve 'Dashatize it' kata

Author: borisskert

src/dashatize-it/dashatize.ts

@@ -0,0 +1,50 @@
+/**
+ * https://www.codewars.com/kata/58223370aef9fc03fd000071/train/typescript
+ */
+export function dashatize (num: number): string {
+  if (isNaN(num)) {
+    return 'NaN'
+  }
+
+  if (num < 0) {
+    return dashatize(-num)
+  }
+
+  const digits = num
+    .toString()
+    .split('')
+    .map(Number)
+
+  const groups = splitBy(digits, (a, b) => {
+    return isOdd(a) || isOdd(b)
+  })
+
+  return groups
+    .map(group => group.join(''))
+    .join('-')
+}
+
+function isOdd (num: number): boolean {
+  return num % 2 === 1
+}
+
+function splitBy<T> (array: T[], predicate: (a: T, b: T) => boolean): T[][] {
+  const splitBetween = (groups: T[][], value: T, i: number): T[][] => {
+    if (i === 0 || !predicate(array[i - 1], value)) {
+      let group = groups[groups.length - 1]
+
+      if (group === undefined) {
+        group = []
+        groups.push(group)
+      }
+
+      group.push(value)
+    } else {
+      groups.push([value])
+    }
+
+    return groups
+  }
+
+  return array.reduce(splitBetween, [])
+}

test/dashatize-it/dashatize.spec.ts

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+import { dashatize } from '../../src/dashatize-it/dashatize'
+import { assert } from 'chai'
+
+function doTest (num: number, expected: string): void {
+  const actual: string = dashatize(num)
+  assert.strictEqual(actual, expected, `Testing for num = ${num}`)
+}
+
+describe('Dashatize it', () => {
+  describe('Sample Tests', () => {
+    it('Basic', () => {
+      doTest(274, '2-7-4')
+      doTest(5311, '5-3-1-1')
+      doTest(86320, '86-3-20')
+      doTest(974302, '9-7-4-3-02')
+    })
+
+    it('Weird', () => {
+      doTest(0, '0')
+      doTest(-1, '1')
+      doTest(-28369, '28-3-6-9')
+    })
+  })
+})