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

Solution 1:

You can't do this without a loop :

function closest (el, predicate) {
  do if (predicate(el)) return el;
  while (el = el && el.parentNode);
}

Well, actually you can, using recursivity (a disguised loop) :

function closest(el, predicate) {
  return predicate(el) ? el : (
     el && closest(el.parentNode, predicate)
  );
}

A demo (using Sizzle for the DOM queries) :

// s = selectors
// n = number of selectors
// get closest s[i+1] from s[i]
// where 0 <= i < n and i % 2 = 0

function main (s) {
  var i, el, from;
  var n = s.length;
  for (i = 0; i < n; i += 2) {
    from = Sizzle(s[i])[0];
    el = closest(from, function (el) {
      return !!el && el !== document && (
        Sizzle.matchesSelector(el, s[i + 1])
      );
    });
    console.log(el);
  }
}

function closest (el, predicate) {
  do if (predicate(el)) return el;
  while (el = el && el.parentNode);
}

main([
  "#winner" , "b", 
  "#winner" , "p", 
  "#winner" , "div", 
  "#winner" , "div:not(#trump)", 
  "#winner" , "#clinton",
  "#looser" , "html"
]);

<script src="https://cdnjs.cloudflare.com/ajax/libs/sizzle/1.10.18/sizzle.min.js"></script>

<div id="main">
  <div id="trump">
    <p>Donald <b id="winner">Trump</b></p>
  </div>
  <div id="clinton">
    <p>Hillary <b>Clinton</b></p>
  </div>
</div>

Solution 2:

To add an updated answer, there is now Element.closest(<query_selector>) available.

https://developer.mozilla.org/en-US/docs/Web/API/Element/closest

This isn't supported on IE, but that mozilla doc page includes code for a polyfill for IE8 and IE9+.

Solution 3:

Concise and quick (tested with Benchmark.js) way to search for closest element by any css selector:

var ep = Element.prototype;
ep.matches = ep.matches || ep.webkitMatchesSelector || ep.msMatchesSelector || ep.mozMatchesSelector;

function getClosest( elem, selector ) {
    while (elem !== document.body) {
        elem = elem.parentElement;
        if (elem.matches(selector)) return elem;
    }
}

Supports IE9+ and the rest of the browsers you can expect to care about.

Solution 4:

function closestById(el, id) {
  while (el.id != id) {
    el = el.parentNode;
    if (!el) {
      return null;
    }
  }
  return el;
}

// Use it like:

yourTarget = closestById(document.getElementById('unique-identifier'),'targetId')
alert(yourTarget.id);

<div id="targetId">
  Finish
  <div>
    <div id="unique-identifier">
      Start
    </div>
  </div>
</div>

This searches upwards, until a certain ID is found. You can also alter the code to find certain classes.

Solution 5:

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);