Return value depends on argument typescript

When working with TypeScript, you may come across a scenario where the return value of a function depends on the type of argument passed to it. In this blog post, we will explore different solutions to handle this situation.

Solution 1: Using function overloading

Function overloading allows you to define multiple function signatures for a single function. TypeScript will then choose the appropriate function implementation based on the argument types.

Here’s an example:

function processValue(value: string): string;
function processValue(value: number): number;
function processValue(value: string | number): string | number {
  if (typeof value === 'string') {
    return value.toUpperCase();
  } else if (typeof value === 'number') {
    return value * 2;
  }
}

const result1 = processValue("hello"); // Returns "HELLO"
const result2 = processValue(5); // Returns 10

In the above code snippet, we have defined three function signatures for the processValue function. The first two signatures specify that the function can accept a string or a number as an argument. The third signature is the actual implementation of the function, which checks the type of the argument and returns the appropriate value.

Solution 2: Using type guards

Type guards allow you to narrow down the type of a variable within a conditional block. By using type guards, you can perform different operations based on the type of the argument.

Here’s an example:

function processValue(value: string | number): string | number {
  if (typeof value === 'string') {
    return value.toUpperCase();
  } else if (typeof value === 'number') {
    return value * 2;
  }
}

const result1 = processValue("hello"); // Returns "HELLO"
const result2 = processValue(5); // Returns 10

In the above code snippet, we have a single function processValue that accepts a string or a number as an argument. Inside the function, we use the typeof operator to check the type of the argument and perform the appropriate operation.

Both solutions mentioned above achieve the same result. The choice between them depends on the complexity of your code and personal preference. Function overloading provides a more explicit way of defining different function signatures, while type guards offer more flexibility and can be used in a wider range of scenarios.

Feel free to choose the solution that best suits your needs and coding style!

That’s it for this blog post! We hope you found the solutions helpful in handling situations where the return value depends on the argument type in TypeScript. Happy coding!

Return value depends on argument typescript