如何将 class 添加和删除到 div 元素平原 javascript

Question

I am trying to add different classes to a div based on what is clicked, which I've managed to do, but need to remove the previously clicked/selected class and replace with the clicked one, Can't seem to get the remove part right. Most of the solutions I've come across are either toggles or adding and removing between two classes, but not 3 or more.

Thanks

This is what I have tried so far and the add part works as expected but when I click a different button it does not remove the previous clicked one

The HTML

<button id="btn-1" data-width="w-1/3">Mobile</button>
<button id="btn-2" data-width="w-2/3">Tablet</button>
<button id="btn-3" data-width="w-full">Desktop</button>

<div class="frame">
  Some Content
</div>

The Javascript

let setMobile = document.querySelector('#btn-1');
let setTablet = document.querySelector('#btn-2');
let setDesktop = document.querySelector('#btn-3');
let btns = [setMobile, setTablet, setDesktop];

function getBtnId(btn) {
    btn.addEventListener('click', function() {
        let frame = document.querySelector('.frame')
        frame.classList.add(this.dataset.width)
        if(frame.classList.contains(btns)){
            frame.classList.remove(this.dataset.width)
        }
        console.log(this.dataset.width);
    });
}

btns.forEach(getBtnId);

Basically, what I am trying to do is a responsive frame which will adjust its width depending on what is clicked.

Answer 1

You can store the current class in a variable and use the remove() to remove the previous class on each click.

 let setMobile = document.querySelector('#btn-1'); let setTablet = document.querySelector('#btn-2'); let setDesktop = document.querySelector('#btn-3'); let btns = [setMobile, setTablet, setDesktop]; var currentClass; function getBtnId(btn) { btn.addEventListener('click', function() { let frame = document.querySelector('.frame') if (currentClass) { frame.classList.remove(currentClass); } currentClass = this.dataset.width; frame.classList.add(currentClass); console.log(this.dataset.width); }); } btns.forEach(getBtnId);

 <button id="btn-1" data-width="w-1/3">Mobile</button> <button id="btn-2" data-width="w-2/3">Tablet</button> <button id="btn-3" data-width="w-full">Desktop</button> <div class="frame"> Some Content </div>

Answer 2

Here's a generalized version to work with multiple elements. I've wrapped each frame and buttons in a section element. Then I've bound the event listeners to the sections and used event bubbling / event delegation to perform the switch. I've also used a data attribute on the target frame to hold the current state.

 function setWidthClass(event) { var newWidth = event.target.dataset.width; //This identifies a button click with our dataset if (newWidth) { //get the target div var target = this.querySelector(".frame"); //if the target has a class set remove it if (target.dataset.width) { target.classList.remove(target.dataset.width); } //Add the new class target.classList.add(newWidth); //Update the data on the target element target.dataset.width = newWidth; } } //Add the event listener var sections = document.querySelectorAll(".varyWidth"); for (var i = 0; i < sections.length; i++) { sections[i].addEventListener("click", setWidthClass); }

 .w-third { color: red; }.w-half { color: blue; }.w-full { color: green; }

 <section class="varyWidth"> <button data-width="w-third">Mobile</button> <button data-width="w-half">Tablet</button> <button data-width="w-full">Desktop</button> <div class="frame"> Some Content </div> </section> <section class="varyWidth"> <button data-width="w-third">Mobile</button> <button data-width="w-half">Tablet</button> <button data-width="w-full">Desktop</button> <div class="frame"> Some Content </div> </section> <section class="varyWidth"> <button data-width="w-third">Mobile</button> <button data-width="w-half">Tablet</button> <button data-width="w-full">Desktop</button> <div class="frame"> Some Content </div> </section>

Answer 3

Rather than track the current class, you can also just reset it:

 let setMobile = document.querySelector('#btn-1'); let setTablet = document.querySelector('#btn-2'); let setDesktop = document.querySelector('#btn-3'); let btns = [setMobile, setTablet, setDesktop]; function getBtnId(btn) { btn.addEventListener('click', function() { let frame = document.querySelector('.frame') // reset the classList frame.classList = ["frame"]; frame.classList.add(this.dataset.width) console.log(this.dataset.width); }); } btns.forEach(getBtnId);

 <button id="btn-1" data-width="w-1/3">Mobile</button> <button id="btn-2" data-width="w-2/3">Tablet</button> <button id="btn-3" data-width="w-full">Desktop</button> <div class="frame"> Some Content </div>