First Block Attempt

block.js

/**
 * Simple block to output a list of posts (as hyperlinked images).
 *
 * Simple block, renders and saves the same content without interactivity.
 *
 */
 var el = wp.element.createElement,
     registerBlockType = wp.blocks.registerBlockType,
     withAPIData = wp.components.withAPIData;

 registerBlockType( 'my-plugin/latest-post', {
     title: 'Latest Post Images',
     icon: 'megaphone',
     category: 'widgets',

     edit: withAPIData( function() {
         return {
             posts: '/traction/v1/posts/2'
         };
     } )( function( props ) {
         if ( ! props.posts.data ) {
             return "loading !";
         }
         if ( props.posts.data.length === 0 ) {
             return "No posts";
         }
         var className = props.className;

	 var posts = props.posts.data;

	 posts.forEach(function(post) {

	         return el(
	             'a', { className: className, href: post.guid },
	             el( 'img', { src: post.featured_image } )
	         );
	 });

     } ),

     save: function() {
         // Rendering in PHP
         return null;
     },
 } );