How do you save a function to call on it later to be executed when a certain promise is fullfilled example beneath

Started coding yesterday and all i know how to use is hide and show functions but so far ive managed to build a very pretty checkout system. On my basic knowledge. But its so many elements to show and hide so I would like to learn how to save a function so the code becomes very short effective simple and light.

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Id like to save this whole part of code beneath to be saved, so I can just call on it later so something like;

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export function StopLineBottom_viewportEnter(event) { “function close checkout” }

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The code I would like to save and recall later:

export function StopLineBottom_viewportEnter(event) {    

$w("#Glass").hide("");    
$w("#CheckoutBox1").hide("");   
$w("#Galasky").hide("");
$w("#PreviewBox").hide("");
$w("#GalaskyStarlight").hide("");
$w("#ProductPreview").hide("");
$w("#Price").hide("");
$w("#Address1").hide("");
$w("#Line1").hide("");
$w("#Country").hide("");
$w("#Line2").hide("");
$w("#City").hide("");
$w("#Line3").hide("");
$w("#Address2").hide("");
$w("#Line4").hide("");
$w("#PostalCode").hide("");
$w("#Line5").hide("");
$w("#Name").hide("");
$w("#Line6").hide("");
$w("#Number").hide("")
$w("#Line7").hide("");
$w("#CheckoutButton").hide("");
$w("#CheckoutBox2").hide("");
$w("#PaymentProviders").hide("");
$w("#CloseButtonIcon").hide("");
$w("#CloseButtonHitbox").hide("");
}