feat: add getDisplayName() and tests

Author: streamich

src/util/__tests__/getDisplayName.test.tsx

@@ -0,0 +1,83 @@
+import {Component} from 'react';
+import {h} from '../../util';
+import getDisplayName from '../getDisplayName';
+
+describe('getDisplayName()', () => {
+  it('is a function', () => {
+    expect(getDisplayName).toBeInstanceOf(Function);
+  });
+
+  it('stateless component', () => {
+    const Comp = () => null;
+
+    expect(getDisplayName(Comp)).toBe('Comp');
+  });
+
+  it('stateless component JSX', () => {
+    const Comp = () => null;
+
+    expect(getDisplayName(<Comp />)).toBe('<Comp>');
+  });
+
+  it('stateless named component', () => {
+    const Comp = function MyComp () {};
+
+    expect(getDisplayName(Comp)).toBe('MyComp');
+  });
+
+  it('stateless named component JSX', () => {
+    const Comp = function MyComp () {
+      return null;
+    };
+
+    expect(getDisplayName(<Comp />)).toBe('<MyComp>');
+  });
+
+  it('class Component', () => {
+    const Comp = class MyComp extends Component {
+      render () {
+        return null;
+      }
+    }
+
+    expect(getDisplayName(Comp)).toBe('MyComp');
+  });
+
+  it('class Component JSX', () => {
+    const Comp = class MyComp extends Component {
+      render () {
+        return null;
+      }
+    }
+
+    expect(getDisplayName(<Comp />)).toBe('<MyComp>');
+  });
+
+  it('class Component renamed', () => {
+    const Comp = class MyComp extends Component {
+      static displayName = 'Foobar';
+
+      render () {
+        return null;
+      }
+    }
+
+    expect(getDisplayName(Comp)).toBe('Foobar');
+  });
+
+  it('class Component renamed JSX', () => {
+    const Comp = class MyComp extends Component {
+      static displayName = 'Foobar';
+
+      render () {
+        return null;
+      }
+    }
+
+    expect(getDisplayName(<Comp />)).toBe('<Foobar>');
+  });
+
+  it('unknown', () => {
+    expect(getDisplayName(123)).toBe('Unknown');
+  });
+});

src/util/getDisplayName.ts

@@ -0,0 +1,16 @@
+const getDisplayName = (Comp: any) => {
+  const tipof = typeof Comp;
+
+  switch (tipof) {
+    case 'string':
+      return Comp;
+    case 'function':
+      return Comp.displayName || Comp.name || 'Unknown';
+    case 'object':
+        return `<${Comp.type.displayName || Comp.type.name || String(Comp)}>`;
+    default:
+      return 'Unknown';
+  }
+}
+
+export default getDisplayName;