I had the need to find out of an element I got via a click event was a descendant of a particular parent element.
I assigned an id to that parent, and I checked if the clicked element belonged to its child elements using this loop:
const isDescendant = (el, parentId) => {
let isChild = false
if (el.id === parentId) { //is this the element itself?
isChild = true
}
while (el = el.parentNode) {
if (el.id == parentId) {
isChild = true
}
}
return isChild
}
document.addEventListener('click', event => {
const parentId = 'mycontainer'
if (isDescendant(event.target, parentId)) {
//it is a descendant, handle this case here
} else {
//it's not a descendant, handle this case here
}
})
In the while loop we use the assignment operator = to iterate until there’s no parent node anymore, in that case el.parentNode returns null and the while loop ends.
It’s a way to go “up” in the elements tree until it finishes.
Download my free JavaScript Beginner's Handbook and check out my JavaScript Masterclass!