DOM / pure JavaScript solution to jQuery.closest() implementation?

Answer 1

Alternative is a recursive function. This is slightly different to closest as i searches the children, I'm not sure if closest does.

function closest(elem) {
    if( elem.className.indexOf("non-unique-identifier") ) {
        return elem;
    } 

    var parent = elem.parentNode;

    for(var i = 0; i< parent.children.length; i++ ) {
        if( parent.children[i].className.indexOf("non-unique-identifier")!=-1)  {
            return parent.children[i];
        }
    }

    return closest(parent);
}



var elem = document.getElementById('unique-identifier');

var cl = closest(elem);

console.log(cl);

Non children searching example (more like closest):

function closest(elem) {
    if( elem.className.indexOf("non-unique-identifier") ) {
        return elem;
    } 

    var parent = elem.parentNode;

    if( parent.className.indexOf("non-unique-identifier")!=-1) {
        return parent;
    }    

    return closest(parent);
}



var elem = document.getElementById('unique-identifier');

var cl = closest(elem);

console.log(cl);