Deconstruct TypeScript objects with Fallback Values

Say we have a TypeScript interface with required and optional values.

interface NonosOptions {
  thickness: number,
  pressure?: number
}

thickness is required, pressure is optional.

If we create an object of type NonosOptions, we can omit pressure but not thickness.

const options: NonosOptions = {
  thickness: 1.5
}

We can now deconstruct our options with a default pressure value, which will only be used if options doesn't define a value.

const { thickness = 2, pressure = 0.75 } = options
// thickness = 1.5
// pressure = 0.75

As you can see, thickness ignores the 2 assignment because options sets it as 1.5. But pressure is set to 0.75 because options doesn't define a pressure value.

If pressure is defined in options, both thickness and pressure deconstruction fallback values would be ignored.

const options: NonosOptions = {
  thickness: 1.5,
  pressure: 0.25
}

const { thickness = 2, pressure = 0.75 } = options
// thickness = 1.5
// pressure = 0.25