fix: Add support for renderable Arrays of strings

src/Helmet.js

@@ -187,7 +187,13 @@ const Helmet = (Component) => class HelmetWrapper extends React.Component {
                 return warn(`Only elements types ${VALID_TAG_NAMES.join(", ")} are allowed. Helmet does not support rendering <${child.type}> elements. Refer to our API for more information.`);
             }
 
-            if (nestedChildren && typeof nestedChildren !== "string") {
+            if (
+                nestedChildren &&
+                typeof nestedChildren !== "string" &&
+                (
+                    !Array.isArray(nestedChildren) || nestedChildren.some(nestedChild => typeof nestedChild !== "string")
+                )
+            ) {
                 throw new Error(`Helmet expects a string as a child of <${child.type}>. Did you forget to wrap your children in braces? ( <${child.type}>{\`\`}</${child.type}> ) Refer to our API for more information.`);
             }
         }

src/HelmetUtils.js

@@ -301,8 +301,8 @@ const handleClientStateChange = (newState) => {
 };
 
 const updateTitle = (title, attributes) => {
-    if (typeof title === "string" && document.title !== title) {
-        document.title = title;
+    if (typeof title !== "undefined" && document.title !== title) {
+        document.title = Array.isArray(title) ? title.join("") : title;
     }
 
     updateAttributes(TAG_NAMES.TITLE, attributes);

test/HelmetDeclarativeTest.js

@@ -46,6 +46,23 @@ describe("Helmet - Declarative API", () => {
                 });
             });
 
+            it("updates page title and allows children containing expressions", (done) => {
+                const someValue = "Some Great Title";
+
+                ReactDOM.render(
+                    <Helmet>
+                        <title>Title: {someValue}</title>
+                    </Helmet>,
+                    container
+                );
+
+                requestIdleCallback(() => {
+                    expect(document.title).to.equal("Title: Some Great Title");
+
+                    done();
+                });
+            });
+
             it("updates page title with multiple children", (done) => {
                 ReactDOM.render(
                     <div>