How to implement "prevUntil" in Vanilla JavaScript without libraries?

Question

I need to implement the functionality of jQuery's prevUntil() method in Vanilla JavaScript.

I've got several <div> elements on the same level:

<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>

I'm trying to use an onclick event to find the event.target's previousSiblings until a certain criteria is reached (for example, a class name match) then stop.

How do I achieve this?

Answer 1

This answer was previously published here in response to a similar question .

There are a few ways to do it.

Either one of the following should do the trick.

// METHOD A (ARRAY.FILTER, STRING.INDEXOF)
var siblings = function(node, children) {
    siblingList = children.filter(function(val) {
        return [node].indexOf(val) != -1;
    });
    return siblingList;
}

// METHOD B (FOR LOOP, IF STATEMENT, ARRAY.PUSH)
var siblings = function(node, children) {
    var siblingList = [];
    for (var n = children.length - 1; n >= 0; n--) {
        if (children[n] != node) {
            siblingList.push(children[n]);
        }  
    }
    return siblingList;
}

// METHOD C (STRING.INDEXOF, ARRAY.SPLICE)
var siblings = function(node, children) {
   siblingList = children;
   index = siblingList.indexOf(node);
   if(index != -1) {
       siblingList.splice(index, 1);
   }
   return siblingList;
}

FYI: The jQuery code-base is a great resource for observing Grade A Javascript.

Here is an excellent tool that reveals the jQuery code-base in a very streamlined way. http://james.padolsey.com/jquery/

Answer 2

Example Using previousElementSibling:

    var className = "needle";
    var element = clickedElement;
    while(element.previousElementSibling && element.previousElementSibling.className != className) {
       element = element.previousElementSibling;
    }
    element.previousElementSibling; // the element or null

Answer 3

Use .children in combination with .parentNode. Then filter the NodeList, after converting it into an array: http://jsfiddle.net/pimvdb/DYSAm/.

var div = document.getElementsByTagName('div')[0];
var siblings = [].slice.call(div.parentNode.children) // convert to array
                 .filter(function(v) { return v !== div }); // remove element itself
console.log(siblings);

Answer 4

How about this:

while ( node = node.previousElementSibling ) {
    if ( ( ' ' + node.className + ' ' ).indexOf( 'foo' ) !== -1 ) {
        // found; do your thing
        break;
    }
}

Don't bother telling me that this doesn't work in IE8...

Answer 5

There is a previousSibling property in the HTML DOM

Here is some reference

http://reference.sitepoint.com/javascript/Node/previousSibling

Answer 6

Just take a look at how jQuery does it.

prevUntil: function( elem, i, until ) {
    return jQuery.dir( elem, "previousSibling", until );
},

Which uses a while / looping function caled dir(). The prevUntil just keeps going until previousSibling is the same as the until element.

dir: function( elem, dir, until ) {
    var matched = [],
        cur = elem[ dir ];

    while ( cur && cur.nodeType !== 9 && (until === undefined || cur.nodeType !== 1 || !jQuery( cur ).is( until )) ) {
        if ( cur.nodeType === 1 ) {
            matched.push( cur );
        }
        cur = cur[dir];
    }
    return matched;
},

Answer 7

You could use indexOf to determine if the index of the siblings are less than the index of the target element:

// jshint esversion: 9

// get the target node
const node = document.querySelector("div:nth-child(3)");

// get the target node's index
const node_index = node.parentNode.indexOf(node);

// get the siblings of the target node
const siblings = node => [...node.parentNode.children].filter(child => 
  child !== node
);
console.log(siblings);

// get the prevUntil
const class_name = "\bmy_class\b";
const prevUntil = siblings.filter((sibling, i) =>
  i < node_index && (sibling.getAttribute("class") || "").includes(class_name)
);
console.log(prevUntil);

Good luck.