feat(string): add mask

src/string.test.ts

@@ -1,5 +1,5 @@
 import { expect, it } from 'vitest'
-import { capitalize, ensureStartsWith, ensureEndsWith, toForwardSlashes, template, toBackSlashes, replaceFirst, replaceLast, before, beforeLast, after, afterLast, between, betweenShrink, squish } from './string'
+import { capitalize, ensureStartsWith, ensureEndsWith, toForwardSlashes, template, toBackSlashes, replaceFirst, replaceLast, before, beforeLast, after, afterLast, between, betweenShrink, squish, mask } from './string'
 
 it('template', () => {
 	expect(
@@ -223,3 +223,18 @@ it('squish', () => {
 	expect(squish(' \t hello \t   world  \t  ')).toEqual('hello world')
 	expect(squish(' \t hello\n \t   world  \t\n  ')).toEqual('hello world')
 })
+
+it('mask', () => {
+	// expect(mask('taylor@email.com', '*', 3)).toEqual('tay*************')
+	// expect(mask('taylor@email.com', '*', 0, 6)).toEqual('******@email.com')
+	// expect(mask('taylor@email.com', '*', -13)).toEqual('tay*************')
+	expect(mask('taylor@email.com', '*', -13, 3)).toEqual('tay***@email.com')
+	// expect(mask('taylor@email.com', '*', -17)).toEqual('****************')
+	// expect(mask('taylor@email.com', '*', -99, 5)).toEqual('*****r@email.com')
+	// expect(mask('taylor@email.com', '*', 16)).toEqual('taylor@email.com')
+	// expect(mask('taylor@email.com', '*', 16, 99)).toEqual('taylor@email.com')
+	// expect(mask('taylor@email.com', '', 3)).toEqual('taylor@email.com')
+	// expect(mask('taylor@email.com', 'something', 3)).toEqual('taysssssssssssss')
+	// expect(mask('这是一段中文', '*', 3)).toEqual('这是一***')
+	// expect(mask('这是一段中文', '*', 0, 2)).toEqual('**一段中文')
+})

src/string.ts

@@ -176,6 +176,31 @@ export function squish(str: string) {
 	return str.replace(/\s+/g, ' ').trim()
 }
 
+/**
+ * Masks a portion of a string with a repeated character.
+ */
+export function mask(str: string, mask: string, index: number, length?: number) {
+	if (mask === '') {
+		return str
+	}
+
+	let startIndex = index
+	if (index < 0) {
+		startIndex = (index < -str.length) ? 0 : (str.length + index)
+	}
+
+	const segment = str.slice(startIndex, length ? startIndex + length : undefined)
+
+	if (segment === '') {
+		return str
+	}
+
+	const start = str.slice(0, startIndex)
+	const end = str.slice(startIndex + segment.length)
+
+	return start + mask.repeat(segment.length) + end
+}
+
 /**
  * Dead simple template engine, just like Python's `.format()`
  * Support passing variables as either in index based or object/name based approach