✨ Add String.startsWith and String.endsWith function

string/endsWith.ts

@@ -0,0 +1,32 @@
+// Copyright 2021-present the Core-fn authors. All rights reserved. MIT license.
+import { curry } from "../deps.ts";
+
+/**
+ * @internal
+ */
+const _endsWith = <T extends string, U extends string>(
+  val: T,
+  target: U,
+): boolean => target.endsWith(val);
+
+/**
+ * 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
+ * ```ts
+ * // Basic
+ * endsWith('world', 'hello world') // true
+ * endsWith('earth', 'hello world') // false
+ * ```
+ *
+ * @category `String`
+ *
+ * @beta
+ */
+const endsWith = curry(_endsWith);
+
+export { _endsWith, endsWith };

string/endsWith_test.ts

@@ -0,0 +1,21 @@
+// Copyright 2021-present the Core-fn authors. All rights reserved. MIT license.
+import { assertEquals } from "../dev_deps.ts";
+import { _endsWith } from "./endsWith.ts";
+
+Deno.test("_endsWith", () => {
+  const table: [string, string, boolean][] = [
+    ["", "", true],
+    ["o", "hello", true],
+    ["world", "hello world", true],
+    ["O", "hello", false],
+    ["earth", "hello world", false],
+    ["Hello", "hello", false],
+  ];
+  table.forEach(([val, target, expected]) => {
+    assertEquals(
+      _endsWith(val, target),
+      expected,
+      `_endsWith(${val}, ${target}) -> ${expected}`,
+    );
+  });
+});

string/mod.ts

@@ -1,2 +1,4 @@
 // Copyright 2021-present the Core-fn authors. All rights reserved. MIT license.
 export { replace } from "./replace.ts";
+export { startsWith } from "./startsWith.ts";
+export { endsWith } from "./endsWith.ts";

string/starsWith.test.ts

@@ -0,0 +1,19 @@
+// Copyright 2021-present the Core-fn authors. All rights reserved. MIT license.
+import { assertEquals } from "../dev_deps.ts";
+import { _startsWith } from "./startsWith.ts";
+
+Deno.test("startsWith", () => {
+  const table: [string, string, boolean][] = [
+    ["", "", true],
+    ["hello", "hello world", true],
+    ["H", "hello", false],
+    ["Hello", "hello", false],
+  ];
+  table.forEach(([val, target, expected]) => {
+    assertEquals(
+      _startsWith(val, target),
+      expected,
+      `startsWith(${val}, ${target}) -> ${expected}`,
+    );
+  });
+});

string/startsWith.ts

@@ -0,0 +1,32 @@
+// Copyright 2021-present the Core-fn authors. All rights reserved. MIT license.
+import { curry } from "../deps.ts";
+
+/**
+ * @internal
+ */
+const _startsWith = <T extends string, U extends string>(
+  val: T,
+  target: U,
+): boolean => target.startsWith(val);
+
+/**
+ * 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
+ * ```ts
+ * // Basic
+ * startsWith('hello', 'hello world') // true
+ * startsWith('good', 'hello world') // false
+ * ```
+ *
+ * @category `String`
+ *
+ * @beta
+ */
+const startsWith = curry(_startsWith);
+
+export { _startsWith, startsWith };