I was surprised by the following behaviour:
const a = {};
a?.b.c; // throws TypeError: Cannot read properties of undefined (reading 'c')
My intention was to use this expression for when a optionally contains b, but if b is present it is expected to contain c. I had expected the expression a?.b.c to evaluate to undefined, and not throw. What expression should I have used?
I did not use a?.b?.c because I wanted it to throw if b did not contain c.
Edit: The code doesn't work as you expected, you will need the following
if (a?.b) { // if b does exist (optional)
const c = a.b.c; // check if c is undefined (compulsary)
}
In your code, the null-safe property access/optional chaining prevents the TypeError and returns a null when you try to call "a?.b", the null is then passed to the next property accessor as "(null).c" which throws an error.
You need the question mark on both a and b to avoid the excecption
const a = {};
a?.b?.c;