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[英]How do I enable a button once two other buttons have been clicked at least once?
[英]How to manipulate an element only if two buttons have been clicked
我想僅將兩個按鈕都單擊時才將box1的背景色更改為紅色。
HTML:
<button id="button1">klick me</button>
<button id="button2">klick me</button>
<div class="box1"></div>
CSS:
.box1 {
width: 150px;
height: 150px;
background-color: blue;
}
.id2 {
background-color: red;
}
JavaScript的:
function changeColor (){
let button1 = document.querySelector('#button1');
let button2 = document.querySelector('#button2');
let box1 = document.querySelector('.box1');
if(this.id === 'button1'){
box1.classList.toggle('id2');
}
}
button1.addEventListener('click', changeColor);
button2.addEventListener('click', changeColor);
先前的代碼按預期工作。 如果單擊了button1,則box1的顏色變為紅色。
因此,我在下面的if語句中嘗試執行以下操作,以實現僅在單擊兩個按鈕后才更改顏色:
if(this.id === 'button1' && this.id === 'button2' ){
box1.classList.toggle('id2');
}
但是不幸的是它沒有用。 我想念什么? 提前致謝!
您可以使用promises完成此操作 :
function once (handler) { return function one ({ type }) { this.removeEventListener(type, one) return handler.apply(this, arguments) } } function when (type, selector) { return new Promise(resolve => { document.querySelector(selector).addEventListener(type, once(resolve)) }) } Promise.all([ when('click', '#button1'), when('click', '#button2') ]).then(function () { document.querySelector('.box1').classList.toggle('id2') })
.box1 { width: 150px; height: 150px; background-color: blue; } .id2 { background-color: red; }
<button id="button1">click me</button> <button id="button2">click me</button> <div class="box1"></div>
如果將promise鏈放入異步函數並使用while
循環,則可以擴展此方法以反復切換。
function once (handler) { return function one ({ type }) { this.removeEventListener(type, one) return handler.apply(this, arguments) } } function when (type, selector) { return new Promise(resolve => { document.querySelector(selector).addEventListener(type, once(resolve)) }) } async function toggler () { const box = document.querySelector('.box1') while (true) { await Promise.all([ when('click', '#button1'), when('click', '#button2') ]) box.classList.toggle('id2') } } toggler()
.box1 { width: 150px; height: 150px; background-color: blue; } .id2 { background-color: red; }
<button id="button1">click me</button> <button id="button2">click me</button> <div class="box1"></div>
嘗試這個
使用Javascript:
var clicks = {
button1: false,
button2: false
}
var box1 = document.querySelector('.box1');
var button1 = document.querySelector('#button1');
var button2 = document.querySelector('#button2');
function clicked(e){
var btn = this.id;
clicks[btn] = true;
if(clicks.button1 && clicks.button2){
//change color
box1.classList.toggle('id2');
// reset object to initial state (if needed)
clicks = {
button1: false,
button2: false
}
}
}
button1.addEventListener('click', clicked);
button2.addEventListener('click', clicked);
編輯:在按鈕而不是onclick
上添加了事件偵聽器
干得好。
每當單擊按鈕時,如果以前從未單擊過,則將其添加到clickedButtons[]
列表中。
添加按鈕后,檢查兩個按鈕是否都在列表中,如果是,請切換css類並清空列表,以便整個過程可以重新開始。 下次單擊兩個按鈕時,顏色將恢復為初始顏色。
const clickedButtons = []; [b1, b2].forEach(btn => btn.addEventListener('click', (e) => { if (clickedButtons.includes(e.target)) return; // button was clicked before clickedButtons.push(e.target); if ([b1, b2].every(b => clickedButtons.includes(b))) { box1.classList.toggle('red'); clickedButtons.length = 0; // empty the list so we can start over } }))
#box1 { width: 150px; height: 150px; background-color: blue; } #box1.red { background-color: red; }
<button id="b1" type="button">klick me</button> <button id="b2" type="button">klick me</button> <div id="box1"></div>
當您單擊一個按鈕時,其click事件監聽器( changeColor
)中的this
將是您剛剛單擊的按鈕的上下文,因此ID只能是一個或另一個,而不是兩者。
您將需要一個狀態對象來跟蹤兩個按鈕,並且當單擊兩個按鈕時,然后執行更改:
let state = {
button1Clicked: false,
button2Clicked: false
};
let button1 = document.querySelector('#button1');
let button2 = document.querySelector('#button2');
let box1 = document.querySelector('.box1');
function changeColor () {
this.id === 'button1'
? state.button1Clicked = true
: state.button2Clicked = true;
if (state.button1Clicked && state.button2Clicked) {
box1.classList.toggle('id2');
}
}
button1.addEventListener('click', changeColor);
button2.addEventListener('click', changeColor);
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