TypeScript - class methods overloading

In this article, we would like to show how to overload method in class in u>TypeScript.

TypeScript supports function overloading syntax that lets to deflate multiple functions with the same name, different arguments and return types. It is required just to provide some functions declarations and one function definition inside class.

Quick solution:

class SomeClass {

    public someMethod(): ResultType;                          // <----- declaration
    public someMethod(a: ArgType1): ResultType;               // <----- declaration
    public someMethod(a: ArgType2, b: ArgType3): ResultType;  // <----- declaration
    // ...

    public someMethod(a?: any, b?: any): ResultType {         // <----- definition
        // ...                                                // <----- definition
    }                                                         // <----- definition
}

// ...

Practical example

class Printer {

    public print(a: string): void;               // <----- declaration
    public print(a: string, b: string): void;    // <----- declaration

    public print(a: string, b?: string): void {  // <----- definition
        if (b) {                                 // <----- definition
            console.log(a + ' ' + b);            // <----- definition
        } else {                                 // <----- definition
            console.log(a);                      // <----- definition
        }                                        // <----- definition
    }                                            // <----- definition
}

const printer = new Printer();

printer.print('Hi!');
printer.print('Hi', 'John!');

Output:

Hi!
Hi John!

See also

1. TypeScript - function overloading