feat(): add new method palindrome (#16)

Author: houssenedao

README.md

@@ -26,13 +26,16 @@ For the majority of the remaining Str documentation
 [contains](#method-contains)
 [ucFirst](#method-ucFirst)
 [lower](#method-lower)
+[palindrome](#method-palindrome)
 
 #### <a name="method-contains"></a> `contains()`
 
 #### <a name="method-ucFirst"></a> `ucFirst()`
 
 #### <a name="method-lower"></a> `lower()`
 
+#### <a name="method-palindrome"></a> `palindrome()`
+
 ## <a name="arr"></a> Array - Arr
 
 ### <a name="aam"></a> Available methods

lib/exceptions/index.ts

@@ -0,0 +1 @@
+export * from './str.exception';

lib/exceptions/str.exception.ts

@@ -0,0 +1,7 @@
+export class StrException extends Error {
+  name: 'StrException';
+
+  constructor(message: string) {
+    super(message);
+  }
+}

lib/str/string.interface.ts

@@ -2,4 +2,5 @@ export interface IString {
   ucFirst(value: string): string;
   contains(value: string, needles: string | string[]): boolean;
   lower(value: string): string;
+  palindrome(value: string): boolean;
 }

lib/str/string.spec.ts

@@ -1,4 +1,5 @@
 import { Str } from './string';
+import { StrException } from '../exceptions';
 
 describe('Str', () => {
   let str = new Str();
@@ -60,4 +61,33 @@ describe('Str', () => {
       expect(str.lower('Hello World!')).toEqual('hello world!');
     });
   });
+
+  describe('Property palindrome', () => {
+    it('should be have property palindrome', () => {
+      expect(str).toHaveProperty('palindrome');
+    });
+
+    it('string is palindrome', () => {
+      expect(str.palindrome('kayak')).toEqual(true);
+      expect(str.palindrome('Kayak')).toEqual(true);
+      expect(str.palindrome('KaYak')).toEqual(true);
+      expect(str.palindrome('kayaK')).toEqual(true);
+      expect(str.palindrome('KayaK')).toEqual(true);
+      expect(str.palindrome('KaYaK')).toEqual(true);
+    });
+
+    it('string is not palindrome', () => {
+      expect(str.palindrome('Hello')).toEqual(false);
+    });
+
+    it('palindrome method return exception if value is more 1 word', () => {
+      expect(() => {
+        str.palindrome('Hello world');
+      }).toThrow('please define a single word');
+
+      expect(() => {
+        str.palindrome('Hello world');
+      }).toThrowError(StrException);
+    });
+  });
 });

lib/str/string.ts

@@ -1,4 +1,5 @@
 import { IString } from './string.interface';
+import { StrException } from '../exceptions';
 
 export class Str implements IString {
   /**
@@ -13,8 +14,8 @@ export class Str implements IString {
 
   /**
    * Determine if a given string contains a given substring.
-   * @param value
-   * @param needles
+   * @param {string} value
+   * @param {string} needles
    * @return boolean
    */
   contains(value: string, needles: string | string[]): boolean {
@@ -23,9 +24,23 @@ export class Str implements IString {
 
   /**
    * Convert the given string to lower-case.
-   * @param value
+   * @param {string} value
+   * @return string
    */
   lower(value: string): string {
     return value.toLowerCase();
   }
+
+  /**
+   * Check string is palindrome.
+   * @param {string} value
+   * @return boolean
+   */
+  palindrome(value: string): boolean {
+    if (value.match(/[\W_]/g)) {
+      throw new StrException(`please define a single word`);
+    }
+
+    return value.toLowerCase() === value.toLowerCase().split('').reverse().join('');
+  }
 }