如何在按向上箭头/向下箭头时将焦点设置到列表项中的上一个/下一个元素 键在 svelte 中?
我想在按下箭头键时将焦点更改为下一个列表项,并在按下键盘上的向上箭头键时将焦点更改为上一个列表项,我已经开始处理一些代码,但它仍然无法正常工作,所以如果有人能帮助我就太好了,在此先感谢
代码:-
<script>
let keyCode;
let item;
function handleKeydown() {
item = document.getElementsByClassName('item');
let itemLength = item.length;
keyCode = event.keyCode;
switch(keyCode){
//ArrowUp
case 38:
//when clicking up arrow focus should move upwards li elements
break;
//ArrowDown
case 40:
//when clicking down arrow focus should move downwards li elements
break;
}
}
</script>
<style>
.item:focus{
border: 1px solid #000000;
}
</style>
<svelte:window on:keydown={handleKeydown} />
<ul>
<li class="item" tabindex="0" >
<p>List Item 1</p>
</li>
<li class="item" tabindex="0" >
<p>List Item 2</p>
</li>
<li class="item" tabindex="0" >
<p>List Item 3</p>
</li>
</ul>
最佳答案
给你,在代码中的注释中进行解释,在答案末尾演示 REPL 链接。
<script>
// dereference the event object, isolating the 'keyCode' property since it's the only one needed
function handleKeydown({ keyCode }) {
// we're only interested in handling up & down arrow keys
if (keyCode !== 38 && keyCode !== 40) return
// currently focused element (if any)
const current = document.activeElement
// get our collection of list elements and turn it into an actual array
const items = [...document.getElementsByClassName('item')]
// attempt to match the currently focused element to an index in our array of list elements
const currentIndex = items.indexOf(current)
// index of the list element to be newly focused
let newIndex
// if the currently focused element was NOT a list item, then default to focusing the first item in the list (index 0)
if (currentIndex === -1) {
newIndex = 0
// otherwise, the currently focused element is an item in our list
} else {
// if the UP key has been pressed, set the new index to the current index minus 1, plus the list size, modulo the list size
if (keyCode === 38) {
newIndex = (currentIndex + items.length - 1) % items.length
// if the DOWN key has been pressed, set the new index to the current index plus 1, modulo the list size
} else {
newIndex = (currentIndex + 1) % items.length
}
}
// blur (= unfocus) the currently focused element (whether it's a list element or not)
current.blur()
// focus the list element at the computed index
items[newIndex].focus()
}
</script>
关于javascript - Svelte:如何在按向上箭头和向下箭头键时将焦点设置到列表项中的上一个/下一个元素?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/63315507/