Typescript 3.7@beta Optional Chaining operator using problem

Question

I'm trying typescript optional chaining operator but throwed this exception.

index.ts:6:1 - error TS2779: The left-hand side of an assignment expression may not be an optional property access. 

My sample code has below

const url = URI({     protocol: 'http',     hostname: 'example.org'  })  // This line throwed document.getElementById('output')?.innerHTML = url.toString() 

How to resolve this problem?

Answer 1

objectVariableName!.propertyName = 'some value to assign'; 

Please note the exclamation symbol i.e,!

Answer 2

const output = document.getElementById('output'); if (output) output.innerHTML = url.toString() 

This operator is made for accessing deep nest values.

Let's look at document.getElementById('output')?.innerHTML. This will return undefined (if '#output' not exists) or string (if '#output' exists). And you trying to assign string to it.

Here you are trying to set a new value for an object property that may not exist.

So yep, optional property access can not be used at the left-hand side of an assignment.

You can read more about it in proposal