I made a simple switch web component with a checked attribute. When I am clicking on the switch it will be set and displayed correctly. When I set the checked property from outside via the button it will be set and displayed correctly as well.
But when I combine these actions the attributes are fine, but it won’t be visually changed anymore when setting ischecked with the button.
I uploaded a fiddle with the described problem: https://jsfiddle.net/axn46okv/
<!DOCTYPE html>
<html>
<head>
<title>Page Title</title>
</head>
<body>
<custom-toggle checked="true"></custom-toggle>
<button onclick="test()">Change State</button>
<script>
function test() {
var toggle = document.querySelector('custom-toggle');
toggle.checked = !toggle.checked;
}
</script>
<script type="module">
const template = document.createElement('template');
template.innerHTML = `
<style>
/* The switch - the box around the slider */
.switch {
position: relative;
display: inline-block;
width: 60px;
height: 34px;
}
/* Hide default HTML checkbox */
.switch input {
opacity: 0;
width: 0;
height: 0;
}
/* The slider */
.slider {
position: absolute;
cursor: pointer;
top: 0;
left: 0;
right: 0;
bottom: 0;
background-color: #ccc;
-webkit-transition: .4s;
transition: .4s;
}
.slider:before {
position: absolute;
content: "";
height: 26px;
width: 26px;
left: 4px;
bottom: 4px;
background-color: white;
-webkit-transition: .4s;
transition: .4s;
}
input:checked + .slider {
background-color: #2196F3;
}
input:focus + .slider {
box-shadow: 0 0 1px #2196F3;
}
input:checked + .slider:before {
-webkit-transform: translateX(26px);
-ms-transform: translateX(26px);
transform: translateX(26px);
}
/* Rounded sliders */
.slider.round {
border-radius: 34px;
}
.slider.round:before {
border-radius: 50%;
}
</style>
<label class="switch">
<input type="checkbox">
<span class="slider round"></span>
</label>
`
export class customToggle extends HTMLElement {
#shadowRoot;
#input;
static get observedAttributes() {
return ['checked', 'enabled'];
}
constructor() {
super();
this.#shadowRoot = this.attachShadow({
mode: 'closed'
});
this.#shadowRoot.appendChild(template.content.cloneNode(true));
this.#input = this.#shadowRoot.querySelector('input');
}
get checked() {
return this.getAttribute('checked') === 'true';
}
set checked(value) {
this.setAttribute('checked', Boolean(value));
this.syncChecked();
}
connectedCallback() {
this.syncChecked();
this.#input.addEventListener("click", () => {
this.checked = !this.checked;
});
}
syncChecked() {
if (this.checked && !this.#input.hasAttribute('checked')) {
this.#input.setAttribute('checked', '');
console.log("addAttribute");
} else if (!this.checked && this.#input.hasAttribute('checked')) {
this.#input.removeAttribute('checked');
console.log("removeAttribute");
}
}
}
window.customElements.define('custom-toggle', customToggle);
</script>
</body>
</html>
2
Answers
I figured it out.
The problem was the way I set the checked attribute:
has to be:
I am still confused why it works initially, but this solves it.
You are missing a
attributeChangedCallback
,So your component never processes a
checked
attribute change by itself.Simplified code: