Void Data Type in TypeScript

The void data type in TypeScript is used to represent the absence of a value. It is primarily used to indicate that a function does not return a value. Understanding how to use void can help you write clearer and more predictable functions.

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Basic Usage

The void type is commonly used as the return type for functions that do not return any value. Here’s a basic example:

function logMessage(message: string): void {
  console.log(message);
}

logMessage("This is a message"); // Output: This is a message

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Functions and Methods for Void

Although the void type itself does not have methods, it is useful to know how to work with functions that have a void return type. Below is a table of common use cases involving void functions:

Function/Method	Description
Function returning void	Defines a function that performs an action but does not return a value.
Callback functions	Functions passed as arguments to other functions that do not return a value.
Event handlers	Functions that handle events (e.g., clicks, key presses) which do not need to return a value.

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Examples of Functions Returning Void

Function Returning Void

Here’s an example of a function that performs an action and does not return a value:

function greet(name: string): void {
  console.log(`Hello, ${name}!`);
}

greet("Alice"); // Output: Hello, Alice!

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Callback Function

Here’s an example of a function that takes a callback function as a parameter. The callback function has a void return type:

function processInput(input: string, callback: (result: string) => void): void {
  const result = input.trim().toUpperCase();
  callback(result);
}

processInput("hello", (result) => {
  console.log(result); // Output: HELLO
});

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Event Handler

Here’s an example of an event handler function with a void return type:

document.getElementById("myButton")?.addEventListener("click", () => {
  console.log("Button clicked!");
});

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Conclusion

The void data type in TypeScript is essential for functions that do not need to return a value. It helps in defining functions that perform actions such as logging, event handling, or executing callbacks. By using void appropriately, you can create clear and concise functions in your TypeScript code.