What is the function of typescript mapping of key to values in events?

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The function of typescript mapping of key to values in events is to provide a way to define the structure of the data being passed within an event. By mapping the key to corresponding values, developers can ensure that the data being passed is consistent and conforms to a certain structure. This can help prevent errors and make it easier to work with the event data in an application. Additionally, by using typescript mapping, developers can take advantage of the benefits of a typed language, such as better code completion and type checking.