The question mark after the variable is called Optional chaining (?.) in JavaScript. The optional chaining operator provides a way to simplify accessing values through connected objects when it’s possible that a reference or function may be undefined or null.
The question mark in JavaScript is commonly used as a conditional operator — called ternary operator when used with a colon (:) and a question mark (?) — to assign a variable name conditionally.
A question mark after variable JavaScript
Simple example code if you are trying to access the properties of a non-declared “obj” object, you will get an error:
<!DOCTYPE html>
<html>
<body>
<script>
console.log(obj?.someProperty);
</script>
</body>
</html>
Output:
But if you have already declared your object and trying to access the property which is Null or undefined, you will get an undefined result :
const obj = {}
console.log(obj?.someProperty);Output: undefined
Source: stackoverflow.com/
Do comment if you have any doubts or suggestions on this JS question topic.
Note: The All JS Examples codes are tested on the Firefox browser and the Chrome browser.
OS: Windows 10
Code: HTML 5 Version