feat: add getDifference for strings

Author: crashmax-dev

src/string.ts

@@ -77,3 +77,33 @@ export function repeatEveryChars(str: string, repeats: number): string {
 
   return result
 }
+
+export interface DifferenceResult {
+  index: number
+  old?: string
+  new?: string
+}
+
+export function getDifference(
+  leftStr: string,
+  rightStr: string
+): DifferenceResult[] {
+  const differenceResult: DifferenceResult[] = []
+  if (leftStr === rightStr) return differenceResult
+
+  for (
+    let index = 0;
+    index < Math.max(leftStr.length, rightStr.length);
+    index++
+  ) {
+    if (leftStr[index] !== rightStr[index]) {
+      differenceResult.push({
+        index: index,
+        old: leftStr[index],
+        new: rightStr[index]
+      })
+    }
+  }
+
+  return differenceResult
+}

test/__snapshots__/string.test.ts.snap

@@ -0,0 +1,71 @@
+// Vitest Snapshot v1, https://vitest.dev/guide/snapshot.html
+
+exports[`getDifference > should return the difference between two strings 1`] = `
+[
+  {
+    "index": 0,
+    "new": "b",
+    "old": "f",
+  },
+  {
+    "index": 1,
+    "new": "a",
+    "old": "o",
+  },
+  {
+    "index": 2,
+    "new": "r",
+    "old": undefined,
+  },
+]
+`;
+
+exports[`getDifference > should return the difference between two strings 2`] = `
+[
+  {
+    "index": 3,
+    "new": "o",
+    "old": undefined,
+  },
+]
+`;
+
+exports[`getDifference > should return the difference between two strings 3`] = `
+[
+  {
+    "index": 0,
+    "new": "f",
+    "old": undefined,
+  },
+  {
+    "index": 1,
+    "new": "o",
+    "old": undefined,
+  },
+  {
+    "index": 2,
+    "new": "o",
+    "old": undefined,
+  },
+]
+`;
+
+exports[`getDifference > should return the difference between two strings 4`] = `
+[
+  {
+    "index": 0,
+    "new": undefined,
+    "old": "f",
+  },
+  {
+    "index": 1,
+    "new": undefined,
+    "old": "o",
+  },
+  {
+    "index": 2,
+    "new": undefined,
+    "old": "o",
+  },
+]
+`;

test/string.test.ts

@@ -1,6 +1,6 @@
 import { describe, expect, test } from 'vitest'
 
-import { capitalize, generateChars, randomToken } from '../src/string.js'
+import { capitalize, generateChars, randomToken, getDifference } from '../src/string.js'
 
 describe('generateChars', () => {
   test('should be defined', () => {
@@ -61,3 +61,16 @@ describe('randomToken', () => {
     }
   })
 })
+
+describe('getDifference', () => {
+  test('should be defined', () => {
+    expect(getDifference).toBeDefined()
+  })
+
+  test('should return the difference between two strings', () => {
+    expect(getDifference('fo', 'bar')).toMatchSnapshot()
+    expect(getDifference('foo', 'fooo')).toMatchSnapshot()
+    expect(getDifference('', 'foo')).toMatchSnapshot()
+    expect(getDifference('foo', '')).toMatchSnapshot()
+  })
+})