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Subscribes a handler function to an event so it runs only once when that event occurs. After the event fires, the handler is automatically removed and is not called again.

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Syntax

instance.once(eventName, handler);

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Parameters

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eventName
string
required
The name of the event to subscribe to.
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handler
function
required
The callback function to run once when the event occurs. Receives (event, instance) as parameters.

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Returns

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void
Returns a void operator.

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Examples

The following examples show different ways to use once: 
// Run handler only on first send
instance.once('pre:send', (event, instance) => {
    console.log('First message being sent');
    event.message.message.content = event.message.message.content.toUpperCase();
});

// Initialize something once when chat is ready
instance.once('chat:ready', (event, instance) => {
    console.log('Performing one-time initialization');
    instance.updateCustomHeaderItems([/* ... */]);
});

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