Implementing functions in Typescript that have duplicate functionality

Question

Implementing functions in Typescript that have duplicate functionality

Within the same Typescript class, I have declared two different function signatures as shown below:

public emit<T1>(event: string, arg1: T1): void {}

and

public emit<T1,T2>(event: string, arg1: T1, arg2: T2): void {}

Despite having a difference in the number of parameters (2 and 3 respectively), an error is triggered during transpilation:

error TS2393: Duplicate function implementation.

My understanding was that overloading functions in TypeScript was possible, given that the parameter count differs in the function signature. Why then am I facing this issue?

javascript typescript

Answer 1

Answer №1

If your code is structured like this:

public emit<T1>(event: string, arg1: T1): void {}
public emit<T1,T2>(event: string, arg1: T1, arg2: T2): void {}
public emit(event: string, ...args: any[]): void {
    // actual implementation here
}

The issue lies in the fact that you have {} after the first 2 lines. This inadvertently creates an empty implementation of a function, similar to:

function empty() {}

What you actually need is to only declare a type for the function, not its implementation. Therefore, replace the empty blocks with just a semi-colon:

public emit<T1>(event: string, arg1: T1): void;
public emit<T1,T2>(event: string, arg1: T1, arg2: T2): void;
public emit(event: string, ...args: any[]): void {
    // actual implementation here
}

Answer 2

If your code is structured like this:

public emit<T1>(event: string, arg1: T1): void {}
public emit<T1,T2>(event: string, arg1: T1, arg2: T2): void {}
public emit(event: string, ...args: any[]): void {
    // actual implementation here
}

The issue lies in the fact that you have {} after the first 2 lines. This inadvertently creates an empty implementation of a function, similar to:

function empty() {}

What you actually need is to only declare a type for the function, not its implementation. Therefore, replace the empty blocks with just a semi-colon:

public emit<T1>(event: string, arg1: T1): void;
public emit<T1,T2>(event: string, arg1: T1, arg2: T2): void;
public emit(event: string, ...args: any[]): void {
    // actual implementation here
}

Answer 3

Answer №2

If you find yourself faced with the challenge of having both Typescript and JavaScript files open in a single window within your IDE, there are three potential solutions to consider:

Option one:

Open either the typescript file or the JavaScript file exclusively.

Second option: execute the following command:

tsc --init

Executing this command will generate a tsconfig.json file for configuring Typescript.

Lastly, another solution is to include

export{}

at the beginning of the file.

Answer 4

If you find yourself faced with the challenge of having both Typescript and JavaScript files open in a single window within your IDE, there are three potential solutions to consider:

Option one:

Open either the typescript file or the JavaScript file exclusively.

Second option: execute the following command:

tsc --init

Executing this command will generate a tsconfig.json file for configuring Typescript.

Lastly, another solution is to include

export{}

at the beginning of the file.

Answer 5

Answer №3

export {}

To include this line in your TypeScript document, simply place it at the very beginning

Answer 6

export {}

To include this line in your TypeScript document, simply place it at the very beginning

Implementing functions in Typescript that have duplicate functionality

Answer №1

Answer №2

Answer №3

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