feat(StyleClassHelper): add putIfPresent method

packages/base/src/styling/StyleClassHelper.test.ts

@@ -0,0 +1,31 @@
+import { StyleClassHelper } from './StyleClassHelper';
+
+describe('StyleClassHelper', () => {
+  test('add class names', () => {
+    const helper = StyleClassHelper.of('class1', 'class2');
+    expect(helper.className).toEqual(`class1 class2`);
+  });
+
+  test('put new classes', () => {
+    const helper = StyleClassHelper.of('firstClass');
+    helper.put('secondClass');
+    expect(helper.className).toEqual(`firstClass secondClass`);
+  });
+
+  test('putIfPresent', () => {
+    const helper = StyleClassHelper.of('firstClass');
+    helper.put('secondClass');
+    helper.putIfPresent('ifPresent1');
+    helper.putIfPresent('ifPresent2', 'ifPresent3');
+    helper.putIfPresent(true === false && 'shouldNotBeThere1', 'a' === 'a' && 'ifPresent4');
+
+    expect(helper.className).toEqual('firstClass secondClass ifPresent1 ifPresent2 ifPresent3 ifPresent4');
+  });
+
+  test('className, toString and valueOf return same value', () => {
+    const helper = StyleClassHelper.of('class1', 'class2');
+    expect(helper.toString()).toEqual(`class1 class2`);
+    expect(helper.valueOf()).toEqual(`class1 class2`);
+    expect(helper.className).toEqual(`class1 class2`);
+  });
+});

packages/base/src/styling/StyleClassHelper.ts

@@ -2,28 +2,40 @@
  * Created by d059190 at 16.03.18
  */
 
-class StyleClassHelper extends String {
+class StyleClassHelper {
   private classes: string[] = [];
 
   constructor(...classes: string[]) {
-    super();
     this.classes = [...classes];
   }
 
-  put(...clazz: string[]) {
+  put(...clazz: string[]): StyleClassHelper {
     this.classes.push(...clazz);
     return this;
   }
 
-  valueOf() {
-    return this.classes.join(' ');
+  putIfPresent(...clazzes: (string | null | undefined)[]): StyleClassHelper {
+    for (const clazz of clazzes) {
+      if (clazz) {
+        this.classes.push(clazz);
+      }
+    }
+    return this;
+  }
+
+  valueOf(): string {
+    return this.className;
   }
 
-  toString() {
-    return this.valueOf();
+  toString(): string {
+    return this.className;
+  }
+
+  get className(): string {
+    return this.classes.join(' ');
   }
 
-  static of(...classes: string[]) {
+  static of(...classes: string[]): StyleClassHelper {
     return new StyleClassHelper().put(...classes);
   }
 }