Ways to enhance focus on childNodes using Javascript

I am currently working on implementing a navigation system using a UL HTML Element.

Here's the code I have so far: 

let htmlUL = <HTMLElement>document.getElementById('autocomplete_ul_' + this.name);
if (arg.keyCode == 40) { // down arrow
    if (this.arrowPosition < htmlUL.childNodes.length)
        this.arrowPosition++;
    console.log(htmlUL.childNodes[this.arrowPosition]);

} else if (arg.keyCode == 38) { //up arrow

    if (this.arrowPosition >= 2)
        this.arrowPosition--;

    console.log(htmlUL.childNodes[this.arrowPosition]);
}

After testing, I can see the correct data in the console when I press UP and DOWN arrows.

However, I am having trouble with 

htmlUL.childNodes[this.arrowPosition].focus()
: 
Property 'focus' does not exist on type 'Node'

Does anyone know how to focus on an element within childNodes? Any help would be greatly appreciated. Thanks!

javascriptangulartypescript

Answer №1

To ensure proper functionality, it is important to cast the child element as type HTMLElement:

const id = `autocomplete_ul_${this.name}`;
const htmlUL = document.getElementById(id) as HTMLElement;

if (arg.keyCode === 40) { // down arrow
    if (this.arrowPosition < htmlUL.childNodes.length) {
      this.arrowPosition++;
    }
} else if (arg.keyCode === 38) { //up arrow
    if (this.arrowPosition >= 2) {
      this.arrowPosition--;
    }
}
const child = htmlUL.childNodes[this.arrowPosition] as HTMLElement;
child.focus();

Side note: Since you have marked your question with the Angular tag, it is advisable to retrieve the list element the angular-way utilizing the ViewChild decorator rather than resorting to document.getElementById.

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