Merge pull request #25 from giraugh/feat/split-array-fn

`splitArray` utility

.changeset/brave-rings-retire.md

@@ -0,0 +1,5 @@
+---
+"@giraugh/tools": minor
+---
+
+Add splitArray util

lib/arrays/index.ts

@@ -6,4 +6,5 @@ export * from './zipArrays'
 export * from './zipArraysLongest'
 export * from './partitionArray'
 export * from './rotateArray'
+export * from './splitArray'
 export * from './splitArrayBy'

lib/arrays/splitArray.ts

@@ -0,0 +1,51 @@
+/**
+ * Split an array when a predicate function determines an element is a predicate
+ * (similiar to String.prototype.split but for arrays)
+ * @param arr the array to split
+ * @param splitFn a function over elements in the array that determines whether an element is a delimeter.
+ * @returns the array of groups split as per the `splitFn`
+ *
+ * @example
+ * const groups = splitArray([1, 3, 5, 6, 7, 9, 11], (x) => x % 2 === 0) // [[1, 3, 5], [7, 9, 11]]
+ */
+export const splitArray = <T>(arr: T[], splitFn: (t: T) => boolean): T[][] => {
+  // Handle special case of empty array
+  if (arr.length === 0) return []
+
+  let groups: T[][] = [[]]
+  while (true) {
+    // Shift one element and peak the next element
+    if (arr.length === 0) break
+    const next = arr.shift()!
+
+    // Split?
+    if (splitFn(next)) {
+      groups.push([])
+    } else {
+      // Add element to current group
+      groups[groups.length - 1]!.push(next)
+    }
+  }
+
+  return groups
+}
+
+if (import.meta.vitest) {
+  const { expect, it } = import.meta.vitest
+
+  it('works for example 1', () => {
+    const runs = splitArray([1, 3, 5, 6, 7, 9, 11], (x) => x % 2 === 0) 
+    expect(runs).toEqual([[1, 3, 5], [7, 9, 11]])
+  })
+
+  it('handles an empty array', () => {
+    const runs = splitArray([], (x) => x === 0) 
+    expect(runs).toEqual([])
+  })
+
+  it('works if predicate is always true', () => {
+    const runs = splitArray(['a', 'b', 'c'], () => true) 
+    expect(runs).toEqual([[], [], [], []])
+  })
+
+}