Add core nodes page to user guide

Author: knolleary

_includes/user-guide-toc.html

@@ -4,13 +4,24 @@
     <li class="tocheader">
         <ul>
             <li class="toctitle active"><a href="/docs/user-guide/">User Guide</a></li>
+            <li {% if page.url contains "/docs/user-guide/projects/" %}class="active"{% endif %}><a href="/docs/user-guide/projects/">Working with projects</a></li>
+            <li {% if page.url == "/docs/user-guide/nodes" %}class="active"{% endif %}><a href="/docs/user-guide/nodes">The core nodes</a></li>
+            <li {% if page.url == "/docs/writing-functions" %}class="active"{% endif %}><a href="/docs/writing-functions">Writing Functions</a></li>
+            <li {% if page.url == "/docs/user-guide/messages" %}class="active"{% endif %}><a href="/docs/user-guide/messages">Working with messages</a></li>
+        </ul>
+    </li>
+    <li class="tocheader">
+        <ul>
+            <li class="toctitle"><span>Running Node-RED</span></li>
             <li {% if page.url == "/docs/configuration" %}class="active"{% endif %}><a href="/docs/configuration">Configuration</a></li>
             <li {% if page.url == "/docs/security" %}class="active"{% endif %}><a href="/docs/security">Security</a></li>
             <li {% if page.url == "/docs/user-guide/logging" %}class="active"{% endif %}><a href="/docs/user-guide/logging">Logging</a></li>
-            <li {% if page.url contains "/docs/user-guide/projects/" %}class="active"{% endif %}><a href="/docs/user-guide/projects/">Working with projects</a></li>
             <li {% if page.url == "/docs/node-red-admin" %}class="active"{% endif %}><a href="/docs/node-red-admin">Command-line Admin</a></li>
-            <li {% if page.url == "/docs/writing-functions" %}class="active"{% endif %}><a href="/docs/writing-functions">Writing Functions</a></li>
-            <li {% if page.url == "/docs/user-guide/messages" %}class="active"{% endif %}><a href="/docs/user-guide/messages">Working with messages</a></li>
+        </ul>
+    </li>
+    <li class="tocheader">
+        <ul>
+            <li class="toctitle"><span>Advanced</span></li>
             <li {% if page.url == "/docs/embedding" %}class="active"{% endif %}><a href="/docs/embedding">Embedding into an existing app</a></li>
         </ul>
     </li>

docs/user-guide/images/node_change.png

@@ -6,15 +6,25 @@ title: User Guide
 
 There's lots more to write in this guide, we're just getting started.
 
+#### Using Node-RED
+
+- [Working with projects](/docs/user-guide/projects)
+- [The core nodes](/docs/user-guide/nodes)
+- [Writing Functions](/docs/writing-functions)
+- [Working with messages](/docs/user-guide/messages)
+
+#### Running Node-RED
+
 - [Configuring Node-RED](/docs/configuration)
 - [Security](/docs/security)
 - [Logging](/docs/user-guide/logging)
-- [Working with projects](/docs/user-guide/projects)
 - [Command-line Admin](/docs/node-red-admin)
-- [Using the Function node](/docs/writing-functions)
-- [Working with messages](/docs/user-guide/messages)
+
+#### Advanced
+
 - [Embedding into an existing app](/docs/embedding)
 
+
 <div class="doc-callout">
 <em>Note</em>:  Parts of the user guide assume the reader is somewhat familiar with
 <strong>JavaScript</strong> (not Java).  There are many online resources to get up

docs/user-guide/images/node_debug.png

@@ -0,0 +1,106 @@
+---
+layout: docs
+toc: user-guide-toc.html
+title: The Core Nodes
+---
+
+The Node-RED palette includes a default set of nodes that are the basic building
+blocks for creating flows. This page highlights the core set you should know about.
+
+All nodes include documentation you can see in the Info sidebar tab when you select a node.
+
+- [Inject](#inject)
+- [Debug](#debug)
+- [Function](#function)
+- [Change](#change)
+- [Switch](#switch)
+
+***
+
+<h3 id="inject"><img alt="Inject node" style="vertical-align: middle" src="/docs/user-guide/images/node_inject.png" width="169px"></h3>
+
+The Inject node can be used to manual trigger a flow by clicking the node's button
+within the editor. It can also be used to automatically trigger flows at regular
+intervals.
+
+The message sent by the Inject node can have its `payload` and `topic` properties
+set.
+
+The `payload` can be set to a variety of different types:
+
+ - a flow or global context property value
+ - a String, number, boolean, Buffer or Object
+ - a Timestamp in milliseconds since January 1st, 1970
+
+***
+
+<h3 id="debug"><img alt="Debug node" style="vertical-align: middle" src="/docs/user-guide/images/node_debug.png" width="169px"></h3>
+
+The Debug node can be used to display messages in the Debug sidebar within the editor.
+
+The sidebar provides a structured view of the messages it is sent, making it easier
+to explore the message.
+
+Alongside each message, the debug sidebar includes information about the time the message
+was received and which Debug node sent it. Clicking on the source node id will reveal
+that node within the workspace.
+
+The button on the node can be used to enable or disable its output. It is recommended
+to disable or remove any Debug nodes that are not being used.
+
+The node can also be configured to send all messages to the runtime log, or to
+send short (32 characters) to the status text under the debug node.
+
+The page on [Working with messages](/docs/user-guide/messages) gives more
+information about using the Debug sidebar.
+
+***
+
+<h3 id="function"><img alt="Function node" style="vertical-align: middle" src="/docs/user-guide/images/node_function.png" width="169px"></h3>
+
+The Function node allows JavaScript code to be run against the messages that are
+passed through it.
+
+A complete guide for using the Function node is available [here](/docs/writing-functions).
+
+***
+
+<h3 id="change"><img alt="Change node" style="vertical-align: middle" src="/docs/user-guide/images/node_change.png" width="169px"></h3>
+
+The Change node can be used to modify a message's properties and set context properties
+without having to resort to a Function node.
+
+Each node can be configured with multiple operations that are applied in order. The
+available operations are:
+
+ - **Set** - set a property. The value can be a variety of different types, or
+   can be taken from an existing message or context property.
+ - **Change** - search and replace parts of a message property.
+ - **Move** - move or rename a property.
+ - **Delete** - delete a property.
+
+When setting a property, the value can also be the result of a [JSONata expression](https://jsonata.org).
+JSONata is a declarative query and transformation language for JSON data.
+
+***
+
+<h3 id="switch"><img alt="Switch node" style="vertical-align: middle" src="/docs/user-guide/images/node_switch.png" width="169px"></h3>
+
+The Switch node allows messages to be routed to different branches of a flow by
+evaluating a set of rules against each message.
+
+The node is configured with the property to test - which can be either a message
+property or a context property.
+
+There are four types of rule:
+
+ - **Value** rules are evaluated against the configured property
+ - **Sequence** rules can be used on message sequences, such as those generated
+   by the Split node
+ - A JSONata **Expression** can be provided that will be evaluated against the
+   whole message and will match if the expression returns a `true` value.
+ - An **Otherwise** rule can be used to match if none of the preceding rules have
+   matched.
+
+The node will route a message to all outputs corresponding to matching rules. But
+it can also be configured to stop evaluating rules when it finds one that matches.

docs/user-guide/images/node_function.png

@@ -5,7 +5,7 @@ title: Writing Functions
 ---
 
 The Function node allows JavaScript code to be run against the messages that are
-passed in and then return zero or more messages to continue the flow.
+passed through it.
 
 The message is passed in as an object called `msg`. By convention it will
 have a `msg.payload` property containing the body of the message.