getElementsByClassName isn't returning all elements

Question

I'm creating a button that I should highlight certain words within a specified class, but I am having issues with it returning all elements within the class. It will only work if I specify an index, so I'm assuming there may be something wrong with the existing "for loop". Any help is appreciated!

This will work, but only "highlights" the first element in the class, of course:

var bodyText = document.getElementsByClassName('test')[0].innerHTML;
for (var i = 0; i < searchArray.length; i++) {
bodyText = doHighlight(bodyText, searchArray[i], highlightStartTag, 
highlightEndTag);}

document.getElementsByClassName('test')[0].innerHTML = bodyText;  
return true;

This will not work at all:

var bodyText = document.getElementsByClassName('test').innerHTML;
for (var i = 0; i < searchArray.length; i++) {
bodyText = doHighlight(bodyText, searchArray[i], highlightStartTag, 
highlightEndTag);}

document.getElementsByClassName('test').innerHTML = bodyText;  
return true;

Answer 1

As you can see getElementsByClassName is pluralized (Elements). Indeed a same class can be assigned to multiple HTML elements. You won't find any way to ommit the [0] and you shouldn't anyway as it might mean you're getting data from the wrong node. If you need data from a specific element that you can ensure is unique then you need to give it an id and use getElementById instead.

Answer 2

If you want to replace multiple words in multiple elements, you need two loops:

const testElements = document.getElementsByClassName('test');
for (const element of testElements) {
    for (const search of searchArray) {
        element.innerHTML = doHighlight(element.innerHTML, search, highlightStartTag, highlightEndTag);
    }
}

Answer 3

You cannot access innerHTML in something which returns an htmlcollection

document.getElementsByClassName('test').innerHTML

Because it's written in plain english: getElementsByClassName . plural .

"Elements" .

with an "s" at the end...

meaning it's a (sort of) Array (anhtmlcollection )