How can I effectively use union and optional types in TypeScript?

How can I effectively use union and optional types in TypeScript?

Union types allow you to define a variable that can hold multiple types, while optional types let you specify that a property may or may not be present.

Can you give me an example of using both in a function?

Sure! Here's a function that takes a parameter which can be either a string or a number, and an optional boolean:

function processValue(value: string | number, flag?: boolean) {
    if (typeof value === 'string') {
        console.log('String value:', value);
    } else {
        console.log('Number value:', value);
    }
    if (flag) {
        console.log('Flag is true!');
    }
}

What happens if I don't provide the optional parameter?

If you don't provide the optional parameter, it will be undefined inside the function. You can check for its presence using an if statement.

Are there any best practices for using these types?

Yes! Always ensure that your union types are clear and meaningful, and use optional types sparingly to avoid confusion in your code.