Anjal Binayak Adhikari

Posted on Oct 4, 2020

Javascript 1o1 - HTMLCollection vs NodeList

#javascript1o1 #javascript

This article was originally posted on my Hashnode Blog

This article covers

Difference between HTMLCollection and NodeList
item & namedItem method of HTMLCollection
Iterating HTMLCollection.
item, values, keys, entries, forEach method of NodeList

HTMLCollection vs NodeList

HTMLCollection is a Dynamic List of Objects of elements whereas the NodeList is static.

For instance

<p> Hii </p>
<p> What's your name ? </p>
<script>
let dynamicCollection = document.getElementsByTagName('p'); 
//returns HTMLCollection
console.log(dynamicCollection);

let staticCollection = document.querySelectorAll('p');
//returns NodeList
console.log(staticCollection)
</script>

Output

Here Both have two <p> elements in the list.

Now let us create another <p> element with DOM.


let additionalP = document.createElement('p');
additionalP.innerHTML = "Where do you live? ";

document.body.appendChild(additionalP);

Now let us again console.log both variables holding the list of <p> elements.

console.log(dynamicCollection);
console.log(staticCollection)

Output:

Now see here, The HTMLCollection is updated automatically while NodeList stays the same. This is the key difference.

HTMLCollection methods

1. item

You can access the members of HTMLCollection i.e element's object, using the item method. It expects the index of the element as a parameter.

console.log(dynamicCollection.item(0));

output

2. namedItem

namedItem expects a parameter and returns the element having id or name given in the parameter.

For example

<p id='greeting'>Hii </p>
<p> How are you </p>

<script>
let elems = document.getElementsByTagName('p');
console.log(elems.namedItem('greeting'));
<script>

Output

HTMLCollection Iterations

You can iterate through each member of HTMLCollection using for loop.

let elements = document.getElementsByTagName('p');

for(let i = 0; i < elements.length; i++){
console.log(elements[i]);
}

NodeList Methods

1. Item

same as HTMLCollection.

let p = document.querySelectorAll('p');
p.item(0); //returns first member of list 

//alternative
p[0] //same as p.item(0)

2. entries

<p>Hii</p>
<p>What's your name ? </p>
<script>
let p = document.querySelectorAll('p');
for(let entry of p.entries()){
    console.log(entry);
}
</script>

Output

entry is an array with [index, element] as shown above

3. keys

<p>Hii</p>
<p>What is your name ? </p>
<script>
let p = document.querySelectorAll('p');
for(let key of p.keys()){
    console.log(key);
}
</script>

Output

Here key is just the key of a member of HTMLCollection.

4. values

<p>Hii</p>
<p>What is your name ? </p>
<script>
let p = document.querySelectorAll('p');
for(let value of p.values()){
    console.log(value);
}
</script>

Output

Here value is the member of HTMLCollection.

5. forEach

<p>Hii</p>
<script>
let p = document.querySelectorAll('p');

p.forEach(function(value,index,nodeList){
    console.log(value);
    console.log(index);
    console.log(nodeList);
    console.log(this);
},'anythingYouWantToReferAsThisInsideTheLoops');

</script>