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Question mark after variable JavaScript | Example code

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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>





question mark after variable JavaScript

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 = {}

Output: undefined


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

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