Invoking a function in TypeScript without providing any arguments

Question

Invoking a function in TypeScript without providing any arguments

const range = (...myData: number[]) => {
  myData.sort();
  return myData[myData.length-1] - myData[0];
}

Codecademy explains that even though the rest parameter type is an array of numbers, it's acceptable to call range() without any arguments and no TypeScript error will be generated. However, this results in a NaN value being returned.

I was under the impression that TypeScript would throw an error if we fail to provide values for a function's arguments, unless they are marked with a ? after their name.

typescript

Answer 1

Answer №1

The rest parameter in JavaScript is unique and powerful. You can read more about how it functions in plain JS here. When using rest parameters, the arguments are automatically stored in a JavaScript Array. If no arguments are provided, an empty array will be returned as the rest parameter.

Answer 2

The rest parameter in JavaScript is unique and powerful. You can read more about how it functions in plain JS here. When using rest parameters, the arguments are automatically stored in a JavaScript Array. If no arguments are provided, an empty array will be returned as the rest parameter.

Answer 3

Answer №2

It is important to always expect at least one argument in your function, as dealing with undefined - undefined can lead to unexpected results such as NaN.

const range = <N extends number, Data extends N[]>(...myData:[N,...Data]) => {
  myData.sort();
  return myData[myData.length-1] - myData[0];
}

range() // This will result in an error
range(2) // This is acceptable
range(2,3) // Another valid use case

If you need more information, you can check out the documentation. For added safety, consider enabling all strict flags in your tsconfig file. One particular flag that could be useful is noUncheckedIndexedAccess.

Answer 4

It is important to always expect at least one argument in your function, as dealing with undefined - undefined can lead to unexpected results such as NaN.

const range = <N extends number, Data extends N[]>(...myData:[N,...Data]) => {
  myData.sort();
  return myData[myData.length-1] - myData[0];
}

range() // This will result in an error
range(2) // This is acceptable
range(2,3) // Another valid use case

If you need more information, you can check out the documentation. For added safety, consider enabling all strict flags in your tsconfig file. One particular flag that could be useful is noUncheckedIndexedAccess.

Invoking a function in TypeScript without providing any arguments

Answer №1

Answer №2

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