This article was originally posted on my Hashnode Blog
This article covers
- Difference between
HTMLCollectionandNodeList -
item&namedItemmethod ofHTMLCollection - Iterating
HTMLCollection. -
item,values,keys,entries,forEachmethod ofNodeList
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>
Output:
The picture is really worth a thousand words, ain't it?
Hope you got a clear understanding of HTMLCollection and NodeList and their differences. If not, comment your query.
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