node-red/packages/node_modules/@node-red/nodes/locales/en-US/function/10-switch.html

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<script type="text/html" data-help-name="switch">
    <p>Route messages based on their property values or sequence position.</p>
    <h3>Details</h3>
    <p>When a message arrives, the node will evaluate each of the defined rules
    and forward the message to the corresponding outputs of any matching rules.</p>
    <p>Optionally, the node can be set to stop evaluating rules once it finds one
    that matches.</p>
    <p>The rules can be evaluated against an individual message property, a flow or global
    context property, environment variable or the result of a JSONata expression.</p>
    <h4>Rules</h4>
    <p>There are four types of rule:</p>
    <ol>
        <li><b>Value</b> rules are evaluated against the configured property</li>
        <li><b>Sequence</b> rules can be used on message sequences, such as those
            generated by the Split node</li>
        <li>A JSONata <b>Expression</b> can be provided that will be evaluated
            against the whole message and will match if the expression returns
            a true value.</li>
        <li>An <b>Otherwise</b> rule can be used to match if none of the preceeding
            rules have matched.</li>
    </ol>
    <h4>Notes</h4>
    <p>The <code>is true/false</code> and <code>is null</code> rules perform strict
       comparisons against those types. They do not convert between types.</p>
    <p>The <code>is empty</code> and <code>is not empty</code> rules can be used to test the length of Strings, Arrays and Buffers, or the number of properties an Object has. Neither rule will pass if the property being tested has a <code>boolean</code>, <code>null</code> 
       or <code>undefined</code> value.</p>
    <h4>Handling message sequences</h4>
    <p>By default, the node does not modify the <code>msg.parts</code> property of messages
       that are part of a sequence.</p>
    <p>The <b>recreate message sequences</b> option can be enabled to generate new message sequences
       for each rule that matches. In this mode, the node will buffer the entire incoming
       sequence before sending the new sequences on. The runtime setting <code>nodeMessageBufferMaxLength</code>
       can be used to limit how many messages nodes will buffer.</p>
</script>