Property id is not defined in type Node in PhpStorm/WebStorm

Question

Php/WebStorm is reporting this wierd warning in my JavaScript code stating that property id is not defined in the element/node. Thing is, the element is a firstChild element fetched from the parent element.

function hideChildAndUpdateID(title) {
    let parent = document.getElementById('parent');
    let child = parent.firstChild;

    // Hiding the child.
    child.style.display = 'none';
    // Temporary ID so we can find it later.
    child.id = 'child-tmp-id'; // Warning occurs here
}

And this is the entire message from Php/WebStorm

Property id is not defined in type Node less... (Ctrl+F1) 
Inspection info: This inspection reports assignments to undefined properties of explicitly type-annotated variables.

This code itself actually works. The child element gets it's id changed to whatever I set it to, but this warning is anoying me.

I have tried using child.setAttribute('id', 'child-tmp-id'), but that did not work properly.

Is there a convention when dealing with firstChild or it's just a Php/WebStorm thingy?

Answer 1

Nodes can be more than just elements and don't necessarily have an id property. Try using firstElementChild instead that returns the first child that is an element:

function hideChildAndUpdateID(title) {
    let parent = document.getElementById('parent');
    let child = parent.firstElementChild;

    // Hiding the child.
    child.style.display = 'none';
    // Temporary ID so we can find it later.
    child.id = 'child-tmp-id'; 
}