Using JS to apply CSS when clicking buttons

Question

I am using a modal that when clicked it should popup full screen. Everything is good, modal pops full screen but the header ( logo + menu ) still shows up.

I'm trying to use JS, so when the modal is clicked i want to apply a z-index to the header and when the close button is clicked i will apply another z-index to fix the header.

the link to be clicked is this:

<a class="vPlay vPlay-btn clickformodal" href="#modal-our-work-1" data-toggle="modal" data-video="241737557"><img src="/wp-content/uploads/2018/04/play1.png" /></a>

Now the JS code is this:

let open = document.selectElementByClassName("clickformodal");
let header = document.selectElementByClassName("mk-header");
let close = document.selectElementByClassName("close");


open.addEventListener('click', function () {
  header.classList.add("headerbefore");
});

close.addEventListener('click', function () {
  header.classList.remove("headerafter");
});

And this is the css that will be applied:

.headerbefore {
   z-index: 1;
 }

.headerafter {
   z-index: 301;
}

The issue here appart that it's not doing what it is supposed too, google chrome shows an error in console saying that let open = document.selectElementByClassName("clickformodal"); is not a function.

What am i doing wrong here?

Help me out please, it's been 2 days that i'm trying to fix this and nothing till now :/

Thanks!!!

xake · Accepted Answer · 2018-04-20 04:45:17Z

2

There are 2 things going wrong here:

it should be getElementsByClassName, not selectElementByClassName
as getElementsByClassName returns an element collection, you need to add [0] at its end, e.g. document.getElementsByClassName("clickformodal")[0]

let open = document.getElementsByClassName("clickformodal")[0];
let header = document.getElementsByClassName("mk-header")[0];
let close = document.getElementsByClassName("close")[0];


open.addEventListener('click', function () {
  header.classList.add("headerbefore");
});

close.addEventListener('click', function () {
  header.classList.remove("headerafter");
});

An option could be to use querySelector() instead

let open = document.querySelector(".clickformodal");
let header = document.querySelector(".mk-header");
let close = document.querySelector(".close");


open.addEventListener('click', function () {
  header.classList.add("headerbefore");
});

close.addEventListener('click', function () {
  header.classList.remove("headerafter");
});

If to add to more than 1, use querySelectorAll() (this sample assume there is as many open as close but only 1 header)

let open = document.querySelectorAll(".clickformodal");
let header = document.querySelector(".mk-header");
let close = document.querySelectorAll(".close");


for (var i = 0; i < open.length; i++) {    
   open[i].addEventListener('click', function () {
       header.classList.add("headerbefore");
   });
}

for (var j=0; j < close.length; j++) {
   close[j].addEventListener('click', function () {
       header.classList.remove("headerbefore");
   });
}

edited Apr 20, 2018 at 4:45

xake

472 silver badges11 bronze badges

answered Apr 18, 2018 at 19:27

Asons

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6 Comments

Asons Over a year ago

@xake Maybe you should do remove("headerbefore"); instead of remove("headerafter");

xake Over a year ago

u are the man! Thank you very much! I hope you have a very nice evening just like mine right now :)))

xake Over a year ago

is there any reason why this JS works great when clicking on 1 modal but when clicking on the second modal it won't work? What do you think it could cause this?

Asons Over a year ago

@xake If you mean you have 2, or more, such modal elements, then yes. The above code sample only finds the first. To find more than 1 you need to use e.g. querySelectorAll() and then loop through the result attaching a listener on each.

xake Over a year ago

Hmm, how do i create the loop ? Wouldn't it work if i have the same classes for all the modules i have as i have around 10 @LGSon

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