Safe navigation operator (?.) or (!.) and null property paths

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! is non-null assertion operator (post-fix expression) – it just saying to type checker that you’re sure that a is not null or undefined.

the operation a! produces a value of the type of a with null and undefined excluded

Optional chaining finally made it to typescript (3.7) 🎉

The optional chaining operator ?. permits reading the value of a property located deep within a chain of connected objects without having to expressly validate that each reference in the chain is valid. The ?. operator functions similarly to the . chaining operator, except that instead of causing an error if a reference is nullish (null or undefined), the expression short-circuits with a return value of undefined. When used with function calls, it returns undefined if the given function does not exist.

Syntax:

obj?.prop // Accessing object's property
obj?.[expr] // Optional chaining with expressions
arr?.[index] // Array item access with optional chaining
func?.(args) // Optional chaining with function calls

Pay attention:

Optional chaining is not valid on the left-hand side of an assignment

const object = {};
object?.property = 1; // Uncaught SyntaxError: Invalid left-hand side in assignment

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