Utilizing the "arguments" built-in keyword effectively in situations where the rest operator is not desired

Question

Utilizing the "arguments" built-in keyword effectively in situations where the rest operator is not desired

Given this function declaration:

    someFunc(): void {
      if(__DEV__) {
        this.someOtherFunc.apply(this, arguments);
      }
    }

When I attempt to call it with parameters, it throws an error resembling the following:

TS2554: Expected 0 arguments, but received 2.

The conventional approach would involve utilizing the rest operator instead of relying on arguments. However, I am hesitant to adopt this method due to my usage of a compilation variable __DEV__, as I wish for the method to be removed during build time when __DEV__ is false. Furthermore, employing the rest operator in TypeScript results in additional code being generated when targeting ES5.

Is there an alternative solution in TypeScript that does not necessitate placing @ts-ignore throughout the code wherever the method is utilized?

typescript

Answer 1

Answer №1

To achieve this, you can specify the method's type in a separate location:

interface CustomObject {
    someFunction(...args: any[]): void; // <==== Define the method's type here
    // ...
}

const customObj: CustomObject = {
    // This is how the method is implemented
    someFunction(): void {
        // Since the `arguments` type doesn't match the expected array type,
        // we need to assert it for compatibility
        this.anotherFunction.apply(this, arguments as unknown as any[]);
    },
    // ...
}

customObj.someFunction(1, 2); // <==== Success

In the example above, I used any[], but ensure to use appropriate types.

Playground demonstration

When targeting ES5, the resulting code is:

"use strict";
var customObj = {
    // This is the implementation of the method
    someFunction: function () {
        // Unfortunately, the `arguments` type does not align with the array type
        // that apply expects, hence the necessity to assert it
        this.anotherFunction.apply(this, arguments);
    },
    // ...
};
customObj.someFunction(1, 2); // Works

Answer 2

To achieve this, you can specify the method's type in a separate location:

interface CustomObject {
    someFunction(...args: any[]): void; // <==== Define the method's type here
    // ...
}

const customObj: CustomObject = {
    // This is how the method is implemented
    someFunction(): void {
        // Since the `arguments` type doesn't match the expected array type,
        // we need to assert it for compatibility
        this.anotherFunction.apply(this, arguments as unknown as any[]);
    },
    // ...
}

customObj.someFunction(1, 2); // <==== Success

In the example above, I used any[], but ensure to use appropriate types.

Playground demonstration

When targeting ES5, the resulting code is:

"use strict";
var customObj = {
    // This is the implementation of the method
    someFunction: function () {
        // Unfortunately, the `arguments` type does not align with the array type
        // that apply expects, hence the necessity to assert it
        this.anotherFunction.apply(this, arguments);
    },
    // ...
};
customObj.someFunction(1, 2); // Works

Utilizing the "arguments" built-in keyword effectively in situations where the rest operator is not desired

Answer №1

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