How to properly check a string for empty value, null or undefined in JavaScript?

Hi everyone! I'm a beginner in JavaScript and writing a simple registration form. I need to check if the user entered a name, email, and password. But I keep getting confused with the checks and getting unexpected results. Here's my current code: ```javascript let userName = document.getElementById('name').value; if (userName == '') { console.log('Name is not filled'); } else { console.log('Hello, ' + userName); } ``` The problem is that if the user didn't enter anything, `userName` is an empty string `""`. But sometimes I get `null` or `undefined` (for example, if the element is not on the page, or I'm working with an API). I tried writing it like this: ```javascript if (userName == null || userName == undefined || userName == '') { // ... } ``` But this looks bulky and ugly. Besides,