Declarative jsx example

10 - More Declarative JSX/01 - Complex Structure.js

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+
+
+// This feature does NOT propose the addition of special templating tags.  It only introduces the ability for tags to bind
+// variables, thereby allowing custom components that can be composed in a way that is more readable and feels more declarative.
+// We assume implementations of "push", "if" and "foreach" tags.  The actual implementation is quite trivial, and
+// implementable by the end user.
+
+
+// Currently, to render a bookstore, you would need the following code...
+var booksData = [{title: "Harry Potter", authors: ["JK Rowling"], ...}, ...];
+return <div>{booksData.map(function(bookData){
+  var authorElements = [];
+  bookData.authors.foreach(function(authorData, idx){
+    authorElements.push(<a href={"http://www.authors.com?id="+author.id} style={{color: 'blue', textDecoration: 'none'}}>{author.name}</a>);
+    if(idx !== bookData.authors.length) authorElements.push(", ");
+  });
+  return <div>
+    <h1>{bookData.title}</h1>
+    By: 
+    { bookData.authors.length === 0 ? <span style={{color: 'gray'}}>Unknown author</span> :  {authorElements}}
+  </div>;
+})}</div>;
+
+
+// The problem is that the code above is complex and hard to follow.  it feels a lot like back in the days when
+// user interfaces were built using an imperative API (like IOS, Swing, etc).
+// In order to generate the comma-separated list of authors for each book, we had to create a new array, iterate over
+// the data, and push elements into the new array, and subsequently put the array of elements into the markup.
+// This was a simple example, but you can imagine this widget becoming much more complicated, and it becoming hard
+// to track what's happening in the user interface
+
+// Now let's try something new.
+
+// Ideally, you could do the same thing in a less imperative way by evaluating variables lazily...
+<push name="books" value={[{title: "Harry Potter", authors: ["JK Rowling"], ...}, ...]}>
+  <div>
+    <foreach element="book" collection={books}>
+      <div>
+        <h1>{title}</h1>
+        By:
+        <iff test={book.authors.length === 0}>
+          <span style={{color: 'gray'}}>Unknown author</span>
+        </iff>
+        <iff test={book.authors.length > 0}>
+          <foreach element="author" index="authorIndex" collection={book.authors} />
+            <a
+              href={"http://www.authors.com?id="+author.id}
+              style={{color: 'blue', textDecoration: 'none'}}>{author.name}
+            </a>
+            <iff test={authorIndex < book.authors.length}>, </iff>
+          </foreach>
+        </iff>
+      </div>
+    </foreach>
+  </div>
+</push>
+
+
+// The declarative example is much more readable.  And the readability benefits grow super-linearly with component complexity.
+
+
+
+// Now suppose we get a request from our designers to insert a <hr> element between each of our book div tags.
+// With the declarative model, it's really easy.
+<push name="books" value={[{title: "Harry Potter", authors: ["JK Rowling"], ...}, ...]}>
+  <div>
+    <foreach element="book" index="bookIndex" collection={books}>
+      <div>
+        <h1>{title}</h1>
+        By:
+        <iff test={book.authors.length === 0}>
+          <span style={{color: 'gray'}}>Unknown author</span>
+        </iff>
+        <iff test={book.authors.length > 0}>
+          <foreach element="author" index="authorIndex" collection={book.authors} />
+            <a
+              href={"http://www.authors.com?id="+author.id}
+              style={{color: 'blue', textDecoration: 'none'}}>{author.name}
+            </a>
+            <iff test={authorIndex < book.authors.length}>, </iff>
+          </foreach>
+        </iff>
+      </div>
+      <iff test={bookIndex < books.length}>
+        <hr />
+      </iff>
+    </foreach>
+  </div>
+</push>
+
+
+// I'll leave it as an exercise for the reader to figure out how to do this with the current imperative-ish code
+// It is an informative exercise, because you realize how tricky it really is once you attempt to modify the code.
+

10 - More Declarative JSX/02 - Tag Implementations.js

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+
+
+// I previously claimed that the implementation of "push", "iff", and "foreach" were trivial.
+// We don't need to provide default implementations, but we should allow for them to exist.
+// Here are my implementations, exact syntax of which is to be determined, but you get the idea
+
+class push {
+  render: function() {
+    return this.context.push(this.props.name, this.props.value, this.children);
+  }
+}
+
+class iff {
+  render: function() {
+    return this.props.test === true ? this.props.children : null;
+  }
+}
+
+class foreach {
+  render: function() {
+    this.props.collection.map(function(element, index) {
+      return (
+        <push name={this.props.element} value={element}>
+          <push name={this.props.index} value={index}>
+            {this.props.children}
+          </push>
+        </push>
+      );
+    });
+  }
+}
+
+// Alternate syntaxes might look less like "traditional jsx" but could allow additional performance
+// benefits (like short-circuit evaluation for children that will never render).
+