CODEWITHSUNDEEP
javascriptdom
DA.
DA.

Reputation: 40691

using javascript's .insertBefore to insert item as last child

I so miss jQuery. I'm working on a project where I need to get my hands dirty with good 'ol plain Javascript again.

I have this scenario:

parent
    child1
    child2
    child3

Via javascript, I want to be able to insert a new node before or after any of those children. While javascript has an insertBefore, there is no insertAfter.

Insert before would work fine on the above to insert a node before any one of those:

parent.insertBefore(newNode, child3)

But how does one insert a node AFTER child3? I'm using this at the moment:

for (i=0,i<myNodes.length,i++){
    myParent.insertBefore(newNode, myNodes[i+1])
}

That is inserting my newNode before the next sibling node of each of my nodes (meaning it's putting it after each node).

When it gets to the last node, myNodes[i+1] become undefined as I'm now trying to access a array index that doesn't exist.

I'd think that'd error out, but it seems to work fine in that in that situation, my node is indeed inserted after the last node.

But is that proper? I'm testing it now in a few modern browsers with no seemingly ill effects. Is there a better way?

Upvotes: 10

Views: 39080

Answers (6)

Gibolt
Gibolt

Reputation: 47197

Modern Solution

If you want to position based on child, simply use before or after

child1.before(newNode)   // [newNode, child1, child2]
// or
child1.after(newNode)    // [child1, newNode, child2]

If you want to position based on parent, use prepend or append

parent.prepend(newNode)  // [newNode, child1, child2]
// or
parent.append(newNode)   // [child1, child2, newNode]

Advanced usage

  1. You can pass multiple values (or use spread operator ...).
  2. Any string value will be added as a text element.

Examples:

child1.after(newNode, "foo")     // [child1, newNode, "foo", child2]

const list = ["bar", newNode]
parent.prepend(...list, "fizz")  // ["bar", newNode, "fizz", child1, child2]

Mozilla Docs

before - after

prepend - append

Can I Use - 95% Mar 2021

Upvotes: 12

eQ19
eQ19

Reputation: 10711

I got this code is work to insert a link item as the last child

var cb=function(){
    //create newnode
    var link=document.createElement('link');
    link.rel='stylesheet';link.type='text/css';link.href='css/style.css';

    //insert after the lastnode
    var nodes=document.getElementsByTagName('link'); //existing nodes
    var lastnode=document.getElementsByTagName('link')[nodes.length-1]; 
    lastnode.parentNode.insertBefore(link, lastnode.nextSibling);
};

var raf=requestAnimationFrame||mozRequestAnimationFrame||
    webkitRequestAnimationFrame||msRequestAnimationFrame;
if (raf)raf(cb);else window.addEventListener('load',cb);

Upvotes: 0

Robert Siemer
Robert Siemer

Reputation: 34737

Pure JavaScript actually has a method for what you want:

parent.appendChild(child_to_be_last)

Upvotes: 33

devildrey33
devildrey33

Reputation: 69

To insert item as a last node use :parentNode.insertBefore(newNode, null);

Upvotes: 6

Zajo
Zajo

Reputation: 372

Also when not iterating through children (just inserting after referenceNode) this might be useful:

parentNode.insertBefore(newNode, referenceNode.nextSibling);

Upvotes: 1

Elian Ebbing
Elian Ebbing

Reputation: 19057

The functionality of insertBefore(newNode, referenceNode) is described as:

Inserts the specified node before a reference node as a child of the current node. If referenceNode is null, then newNode is inserted at the end of the list of child nodes.

And since myNodes[i+1] is outside of the array bounds, it returns undefined, which is treated as null in this case. This means you get your desired behavior.

Edit: Link to the W3 specification of insertBefore()

Upvotes: 24

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