node-red/packages/node_modules/@node-red/nodes/locales/en-US/function/89-trigger.html

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<script type="text/html" data-help-name="trigger">
    <p>When triggered, can send a message, and then optionally a second message, unless extended or reset.</p>

    <h3>Inputs</h3>
    <dl class="message-properties">
        <dt class="optional">reset</dt>
        <dd>If a message is received with this property, any timeout or repeat
        currently in progress will be cleared and no message triggered.</dd>
    </dl>

    <h3>Details</h3>
    <p>This node can be used to create a timeout within a flow. By default, when
    it receives a message, it sends on a message with a <code>payload</code> of <code>1</code>.
    It then waits 250ms before sending a second message with a <code>payload</code> of <code>0</code>.
    This could be used, for example, to blink an LED attached to a Raspberry Pi GPIO pin.</p>
    <p>The payloads of each message sent can be configured to a variety of values, including
    the option to not send anything. For example, setting the initial message to <i>nothing</i> and
    selecting the option to extend the timer with each received message, the node will
    act as a watchdog timer; only sending a message if nothing is received within the
    set interval.</p>
    <p>If set to a <i>string</i> type, the node supports the mustache template syntax.</p>
    <p>If the node receives a message with a <code>reset</code> property, or a <code>payload</code>
    that matches that configured in the node, any timeout or repeat currently in
    progress will be cleared and no message triggered.</p>
    <p>The node can be configured to resend a message at a regular interval until it
    is reset by a received message.</p>
    <p>Optionally, the node can be configured to treat messages as if they are separate streams,
    using a msg property to identify each stream. Default <code>msg.topic</code>.</p>
</script>