Destructure Optional Params in Typescript

May 06, 2021

Sometimes you have a function with an optional Object argument that you want to destructure in the function. Like so:

interface SomeObject {
  option1: boolean;
  stuff: boolean;
}

function foo(param?: SomeObject) {
  const { stuff } = param;
}

However you’ll get an error because param could be undefined and TS doesn’t like you trying to destructure something that’s undefined. There are a couple ways around this…

Define a fallback in the initializer and don’t use the ? optional identifier:

function foo(param: SomeObject = {}) {
  const { stuff } = param;
}

Use nullish coalescence:

function foo(param?: SomeObject) {
  const { stuff } = param ?? {};
}

Or just call the propery on the parameter directly with optional chaining:

function foo(param?: SomeObject) {
  anotherFunction(param?.stuff);
}

All of these work and will handle param being undefined.


Written by Matt Gregg, a UI engineer who lives and works in Minneapolis, MN

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