✨ Add startsWith and endsWith functions

src/endsWith.ts

@@ -0,0 +1,35 @@
+import { isString } from '@/isString'
+import { StringWith } from '@/startsWith'
+
+type endsWith<T extends string | undefined = undefined> = StringWith<
+  'endsWith',
+  T
+>
+
+/**
+ * Checks if a string ends with the provided substring.
+ * @param val - search string
+ * @param target - target string
+ * @returns The result of `target.endsWith(val)`
+ *
+ * @example
+ * Basic
+ * endsWith('world', 'hello world') // true
+ * endsWith('earth', 'hello world') // false
+ *
+ * @example
+ * Curry
+ * const endsWithTs = endsWith('ts')
+ * endsWithTs('index.ts') // true
+ */
+const endsWith = <T extends string, U extends string | undefined = undefined>(
+  val: T,
+  target?: U
+): endsWith<U> => {
+  if (isString(target)) {
+    return target.endsWith(val) as endsWith<U>
+  }
+  return ((_target: string) => endsWith(val, _target)) as endsWith<U>
+}
+
+export { endsWith }

src/index.ts

@@ -13,6 +13,7 @@ export { isString } from '@/isString'
 export type { IsSymbol } from '@/isSymbol'
 export { isSymbol } from '@/isSymbol'
 export { multiply } from '@/multiply'
+export { startsWith } from '@/startsWith'
 export { subtract } from '@/subtract'
 export { toLower } from '@/toLower'
 export { toUpper } from '@/toUpper'

src/startsWith.ts

@@ -0,0 +1,42 @@
+import { isString } from '@/isString'
+
+type StringWith<
+  T extends 'startsWith' | 'endsWith',
+  U extends string | undefined = undefined
+> = U extends undefined
+  ? (target: string) => ReturnType<string[T]>
+  : ReturnType<string[T]>
+
+type StartsWith<T extends string | undefined = undefined> = StringWith<
+  'startsWith',
+  T
+>
+
+/**
+ * Checks if a string starts with the provided substring.
+ * @param val - search string
+ * @param target - target string
+ * @returns The result of `target.startsWith(val)`
+ *
+ * @example
+ * Basic
+ * startsWith('hello', 'hello world') // true
+ * startsWith('good', 'hello world') // false
+ *
+ * @example
+ * Curry
+ * const startWithSlash = startsWith('/')
+ * startWithSlash('/path/to') // true
+ */
+const startsWith = <T extends string, U extends string | undefined = undefined>(
+  val: T,
+  target?: U
+): StartsWith<U> => {
+  if (isString(target)) {
+    return target.startsWith(val) as StartsWith<U>
+  }
+  return ((_target: string) => startsWith(val, _target)) as StartsWith<U>
+}
+
+export { startsWith }
+export type { StringWith }

test/endsWith.spec.ts

@@ -0,0 +1,16 @@
+import { endsWith } from '@/endsWith'
+
+describe('endsWith', () => {
+  const table: [string, string, boolean][] = [
+    ['', '', true],
+    ['o', 'hello', true],
+    ['world', 'hello world', true],
+    ['O', 'hello', false],
+    ['earth', 'hello world', false],
+    ['Hello', 'hello', false]
+  ]
+
+  it.each(table)('endsWith(%s, %s) -> %s', (val, target, expected) => {
+    expect(endsWith(val, target)).toBe(expected)
+  })
+})

test/starsWith.spec.ts

@@ -0,0 +1,14 @@
+import { startsWith } from '@/startsWith'
+
+describe('startsWith', () => {
+  const table: [string, string, boolean][] = [
+    ['', '', true],
+    ['hello', 'hello world', true],
+    ['H', 'hello', false],
+    ['Hello', 'hello', false]
+  ]
+
+  it.each(table)('startsWith(%s, %s) -> %s', (val, target, expected) => {
+    expect(startsWith(val, target)).toBe(expected)
+  })
+})