Inquiring about the application of spread argument in TypeScript

Question

Inquiring about the application of spread argument in TypeScript

Here is some code I'm working on:

import _ from 'lodash';

function test(num1: number, num2: number) {
    console.log(num1, num2);
}

test(..._.take(_.shuffle([0, 1, 2]), 2));

I encountered a TS2556 error while using the TS playground and VSCode.

The error message says: "A spread argument must either have a tuple type or be passed to a rest parameter. (ts2556)"

A similar TS2556 error came up when using repl.it as well.

The error message on repl.it reads: "error TS2556: Expected 2 arguments, but got 0 or more."

Currently, I'm unsure about how to address this issue.

typescript lodash spread-syntax

Answer 1

Answer №1

It is recommended to utilize the spread operator when anticipating, as indicated by the error message, 0 or more parameters. Given that your function specifically requires 2 parameters - no more, no less, it would be more appropriate to write:

const myArray = _.take(_.shuffle([0, 1, 2]), 2);

test(myArray[0], myArray[1]);

Ensure to include a validation check just in case (especially if unaware of the array contents passed to shuffle) by verifying whether it contains these two values to prevent any runtime errors.

An exemplary scenario for employing rest parameters:

const myFunction = (requiredParameter: number, ...someOtherOptionalParams: number[]) => {
  someOtherOptionalParams.map(param => {
    // perform actions with optional parameters, if present
  })
}

Your code would also function effectively if both parameters were optional:

function test(num1?: number, num2?: number) {
    console.log(num1, num2);
}

This implies that the function would handle the initial two values from your array, if existing, and then proceed accordingly.

Answer 2

It is recommended to utilize the spread operator when anticipating, as indicated by the error message, 0 or more parameters. Given that your function specifically requires 2 parameters - no more, no less, it would be more appropriate to write:

const myArray = _.take(_.shuffle([0, 1, 2]), 2);

test(myArray[0], myArray[1]);

Ensure to include a validation check just in case (especially if unaware of the array contents passed to shuffle) by verifying whether it contains these two values to prevent any runtime errors.

An exemplary scenario for employing rest parameters:

const myFunction = (requiredParameter: number, ...someOtherOptionalParams: number[]) => {
  someOtherOptionalParams.map(param => {
    // perform actions with optional parameters, if present
  })
}

Your code would also function effectively if both parameters were optional:

function test(num1?: number, num2?: number) {
    console.log(num1, num2);
}

This implies that the function would handle the initial two values from your array, if existing, and then proceed accordingly.

Inquiring about the application of spread argument in TypeScript

Answer №1

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