CODEWITHSUNDEEP
javascripthtmlcssvariablesstyles
Moe
Moe

Reputation: 115

How can I change CSS variable on button click?

How can I make CSS change the button's box-shadow from var('--out') to var('--in') on button click, and when you click it again it'll change back to --out?

I tried doing it but whenever I click the button it just removes the whole shadow.

const btn = document.querySelector('button')
const state = '--out'
btn.addEventListener('click', _ =>{
    document.documentElement.style.setProperty(state, '--in')
})
:root{
--in: inset 25px 25px 60px rgba(0,0,0,.5);
--out: inset -25px -25px 60px rgba(0,0,0,.5);
}
.color_1{
background-color: blue;
border-radius: 200px;
height: 300px;
width: 300px;
box-shadow: var(--out);
}
<body>
<section>
<button class="color_1"/>
</section>
</body>

Upvotes: 4

Views: 4922

Answers (4)

pepitoenpeligro
pepitoenpeligro

Reputation: 44

You can define two possible states and toogle between them.

<body>
    <style>
        :root{
            --in: inset 25px 25px 60px rgba(0,0,0,.5);
            --out: inset -25px -25px 60px rgba(0,0,0,.5);
            --one: blue;
            --two: red;
        }
        .color_1{
            background-color: var(--one);
            border-radius: 200px;
            height: 300px;
            width: 300px;
            box-shadow: var(--in);
        }

        .color_2{
            background-color: var(--two);
            border-radius: 200px;
            height: 300px;
            width: 300px;
            box-shadow: var(--out);
        }
    </style>
    
<section>
<button class="color_1">

</button>

<script>
    const btn = document.querySelector('button')
    const state = '--out'
    btn.addEventListener('click', _ =>{
        states = ['color_1', 'color_2']
        actualClassName = btn.classList[0]
        btn.classList.remove(actualClassName)
        if (actualClassName === states[0]){
            btn.classList.add(states[1])
        } 
        else{
            btn.classList.add(states[0])
        }
    })
</script>

</section>
</body>

Demo

Finally, the best solution would be toogle only the state you desire, like this:

<body>
    <style>
        :root{
            --in: inset 25px 25px 60px rgba(0,0,0,.5);
            --out: inset -25px -25px 60px rgba(0,0,0,.5);
            --one: blue;
            --two: red;
        }

        .color_1{
            background-color: blue;
            border-radius: 200px;
            height: 300px;
            width: 300px;
        }

        .state1{
            box-shadow: var(--out);
        }
        
        .state2{
            box-shadow: var(--in);
        }
    </style>
    
<section>
<button class="color_1 state1">

</button>

<script>
    const btn = document.querySelector('button')
    const state = '--out'
    btn.addEventListener('click', _ =>{
        btn.classList.toggle('state2');
    });
</script>

</section>
</body>

Upvotes: 0

Lisa Broadhead
Lisa Broadhead

Reputation: 1

Ok here's what I got for you!

  1. It was removing --out value and setting it to --in looked like this (--out: --in;). Which is why we were seeing the box-shadow being removed

  2. This code: document.documentElement - was not targeting your button background - change it to: btn.style.boxShadow

const btn = document.querySelector('button');
   const state = '--out'
   btn.addEventListener('click', _ =>{
       document.documentElement.style.boxShadow = 'var(--in)';
   })

Upvotes: 0

Tushar Shahi
Tushar Shahi

Reputation: 20421

You are trying to change the value of one variable with another variable.

You will need getComputedStlye():

:root{
    --in: inset 25px 25px 60px red;
    --out: inset -25px -25px 60px green;
}
.color_1{
    background-color: blue;
    border-radius: 200px;
    height: 300px;
    width: 300px;
    box-shadow: var(--out);
}
<body>
<section>
<button class="color_1">

</button>

<script>
    const btn = document.querySelector('button')
    const state = '--out'
    btn.addEventListener('click', _ =>{  document.documentElement.style.setProperty(state, getComputedStyle(document.documentElement).getPropertyValue('--in'));
    });
</script>

</section>
</body>

But the ideal way would not be to change the value of your root variable. What if you need that value somewhere else. You can have separate classes for this on your element, which you add/toggle on a conditional basis.

:root{
    --in: inset 25px 25px 60px red;
    --out: inset -25px -25px 60px green;
}
.color_1{
    background-color: blue;
    border-radius: 200px;
    height: 300px;
    width: 300px;
}

.shadow1{
    box-shadow: var(--out);
}
.shadow2{
    box-shadow: var(--in);
}
<body>
<section>
<button class="color_1 shadow1">

</button>

<script>
    const btn = document.querySelector('button')
    const state = '--out'
    btn.addEventListener('click', function() {
    //this.classList.remove('shadow1');
    this.classList.toggle('shadow2');
    });
</script>

</section>
</body>

Upvotes: 2

Justiniscoding
Justiniscoding

Reputation: 721

You need to use the :root selector with document.querySelector instead of document.documentElement to change the css variable. You also need to change the css to use a new --state variable that you can toggle between --in and --out with the JS code. You will also need to use getProperty to get the value of the --in or --out css variable before changing it. The following code in the script tag should fix your problem:

const btn = document.querySelector('button')
const state = '--in'
btn.addEventListener('click', _ =>{
    var root = document.querySelector(":root")
    root.style.setProperty("--state", root.style.getProperty(state))
})

And also using the following in your style tag:

:root{
    --in: inset 25px 25px 60px rgba(0,0,0,.5);
    --out: inset -25px -25px 60px rgba(0,0,0,.5);
    --state: var(--out);
}
.color_1{
    background-color: blue;
    border-radius: 200px;
    height: 300px;
    width: 300px;
    box-shadow: var(--state);
}

Upvotes: 0

Related Questions