Getting Started With Using TypeScript's Static Polymorphism

Working with TypeScript’s Static Polymorphism

TypeScript is an open-source programming language developed and maintained by Microsoft. It is a strict syntactical superset of JavaScript, and adds optional static typing to the language. One of its most powerful features is static polymorphism, which is used to create greater type safety. In this article, we'll discuss what static polymorphism is and how it can be used in TypeScript.

What is Static Polymorphism?

Static polymorphism, also known as compile-time polymorphism, is a form of polymorphism where the code is written at compile time and, therefore, known at compile time. In other words, the code that will be executed at runtime is resolved during the compilation process. This can provide many benefits, such as improved type safety and reduced complexity when writing code.

How Does Static Polymorphism Work in TypeScript?

TypeScript makes use of static polymorphism to define a set of related functions that behave differently with respect to their types. For example, you can define a function such as the following:

function func(x: string): string {
  return x + "!";
}

This function will accept a string parameter and will return a string. However, you can also define the same function to accept multiple types, as follows:

function func(x: number | string): any {
  if (typeof x === "string") {
    return x + "!";
  } else if (typeof x === "number") {
    return x * 10;
  }
}

This function will behave differently depending on the type of the input parameter. If the input parameter is a string, the function will return a string with an exclamation mark appended to the end. If the input parameter is a number, the function will return a number multiplied by 10.

By making use of static polymorphism, the TypeScript compiler is able to determine the type of the input parameter and choose the correct behavior at compile time, greatly improving type safety and reducing complexity.

Example of Static Polymorphism

Let's look at a more complex example that demonstrates the power of static polymorphism. Consider the following code:

interface Animal {
  speak(): string;
}

class Cat implements Animal {
  speak(): string {
    return 'Meow';
  }
}

class Dog implements Animal {
  speak(): string {
    return 'Woof';
  }
}

function makeNoise(animal: Animal): string {
  return animal.speak();
}

The makeNoise function takes in an Animal object as a parameter and calls its speak method. But, because we're using static polymorphism, the TypeScript compiler will know at compile time which version of the speak method to call based on the type of the object passed in. If we pass in a Cat object, the compiler will know to call the speak method of the Cat class. Similarly, if we pass in a Dog object, the compiler will know to call the speak method of the Dog class.

Conclusion

Static polymorphism is a powerful feature of TypeScript that provides type safety and reduces complexity. By leveraging the power of the TypeScript compiler, we can create functions that can behave differently depending on the type of the input parameter. This allows us to write code that is safer and easier to read and maintain.