See how we read data from input elements:
document.getElementById("zipCode") as HTMLInputElement
The as HTMLInputElement construct is basically casting a result into the HTMLInputElement class.
Using as directly is not advisable because it can give you ClassCastException; a proper way to use it is as? HTMLInputElement. This returns null if the class cast fails. And Kotlin will force you to use a Null Safety operator from that very moment.
