merge: Add lower (TheAlgorithms#863)

Author: Yatin-kathuria

String/Lower.js

@@ -0,0 +1,28 @@
+/**
+ * @function lower
+ * @description Will convert the entire string to lowercase letters.
+ * @param {String} url - The input URL string
+ * @return {String} Lowercase string
+ * @example lower("HELLO") => hello
+ * @example lower("He_llo") => he_llo
+ */
+
+const lower = (str) => {
+  if (typeof str !== 'string') {
+    throw new TypeError('Invalid Input Type')
+  }
+
+  let lowerString = ''
+
+  for (const char of str) {
+    let asciiCode = char.charCodeAt(0)
+    if (asciiCode >= 65 && asciiCode <= 90) {
+      asciiCode += 32
+    }
+    lowerString += String.fromCharCode(asciiCode)
+  }
+
+  return lowerString
+}
+
+export { lower }

String/test/Lower.test.js

@@ -0,0 +1,9 @@
+import { lower } from '../Lower'
+
+describe('Lower', () => {
+  it('return uppercase strings', () => {
+    expect(lower('hello')).toBe('hello')
+    expect(lower('WORLD')).toBe('world')
+    expect(lower('hello_WORLD')).toBe('hello_world')
+  })
+})