Allow exclusively certain type to pass through the function

Is it possible to receive an error message from the function in the following example? I have included comments at a relevant spot in the code below:

interface Pos {
  x: number,
  y: number,
}

function doSome(pos: Pos) {
  return pos.x + pos.y
}

let pos = {
  x: 1,
  y: 2,
  z: 3,
}

// How can we trigger an error message from this function?
// The 'pos' object contains property 'z', which 
// is not part of the 'Pos' interface.
// We aim to enforce strict typing by ensuring that 
// the variable 'pos' aligns with the 'Pos' interface.
let p = doSome(pos)

Answer №1

When using TypeScript, it only verifies the necessary properties specified in the interface. This implies that if you have 'x' and 'y', it will suffice to execute the function. Additional literals are permitted without causing an error.

If you intentionally want an error, consider adding an extra literal in a function that is not defined in the interface. Doing so will prompt an error notification.

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