fix: Serialize defaultChecked & defaultSelected (#224)

* fix: Serialize defaultChecked as checked attr

* docs: Adding changeset

* fix: Serialize defaultSelected as selected attr

Author: rschristian

.changeset/cyan-students-unite.md

@@ -0,0 +1,5 @@
+---
+'preact-render-to-string': patch
+---
+
+Ensures `defaultChecked` is serialized as `checked` attribute

src/index.js

@@ -15,7 +15,8 @@ const SHALLOW = { shallow: true };
 // components without names, kept as a hash for later comparison to return consistent UnnamedComponentXX names.
 const UNNAMED = [];
 
-const VOID_ELEMENTS = /^(area|base|br|col|embed|hr|img|input|link|meta|param|source|track|wbr)$/;
+const VOID_ELEMENTS =
+	/^(area|base|br|col|embed|hr|img|input|link|meta|param|source|track|wbr)$/;
 
 const UNSAFE_NAME = /[\s\n\\/='"\0<>]/;
 
@@ -258,10 +259,14 @@ function _renderToString(vnode, context, opts, inner, isSvgMode, selectValue) {
 
 			if (name === 'defaultValue') {
 				name = 'value';
+			} else if (name === 'defaultChecked') {
+				name = 'checked';
+			} else if (name === 'defaultSelected') {
+				name = 'selected';
 			} else if (name === 'className') {
 				if (typeof props.class !== 'undefined') continue;
 				name = 'class';
-			} else if (isSvgMode && name.match(/^xlink:?./)) {
+			} else if (isSvgMode && /^xlink:?./.test(name)) {
 				name = name.toLowerCase().replace(/^xlink:?/, 'xlink:');
 			}
 

test/render.test.js

@@ -95,6 +95,20 @@ describe('render', () => {
 			expect(rendered).to.equal(expected);
 		});
 
+		it('should serialize defaultChecked prop to the checked attribute', () => {
+			let rendered = render(<input type="checkbox" defaultChecked />),
+				expected = `<input type="checkbox" checked />`;
+
+			expect(rendered).to.equal(expected);
+		});
+
+		it('should serialize defaultSelected prop to the selected attribute', () => {
+			let rendered = render(<option defaultSelected />),
+				expected = `<option selected></option>`;
+
+			expect(rendered).to.equal(expected);
+		});
+
 		it('should include boolean aria-* attributes', () => {
 			let rendered = render(<div aria-hidden aria-whatever={false} />),
 				expected = `<div aria-hidden="true" aria-whatever="false"></div>`;