如何在进度条中添加计时器

Question

我想添加一个计时器，它会自动减少(比如10秒、9秒……直到0秒(，但进度条会增加。我是javascript的新手，下面的代码也是从另一个网站复制的，所以请帮助我在进度条中添加计时器

直到现在我做了这个代码

我想这样做演示

<div class="progress"></div>
<style>
.progress-bar {
height: 20px;
background: #1da1f2;
box-shadow: 2px 14px 15px -7px rgba(30, 166, 250, 0.36);
border-radius: 50px;
transition: all 0.5s;
}
.progress {
width: 100%;
display: flex;
flex-flow: column nowrap;
justify-content: center;
align-items: start;
background: #e6e9ff;
border-radius: 20px;
box-shadow: 0px 10px 50px #abb7e9;
}
</style>
<script>
/* 
* (class)Progress<nowValue, minValue, maxValue>
*/
//helper function-> return <DOMelement>
function elt(type, prop, ...childrens) {
let elem = document.createElement(type);
if (prop) Object.assign(elem, prop);
for (let child of childrens) {
if (typeof child == "string") elem.appendChild(document.createTextNode(child));
else elem.appendChild(elem);
}
return elem;
}
//Progress class
class Progress {
constructor(now, min, max, options) {
this.dom = elt("div", {
className: "progress-bar"
});

this.min = min;
this.max = max;
this.intervalCode = 0;
this.now = now;
this.syncState();
if(options.parent){
document.querySelector(options.parent).appendChild(this.dom);
} 
else document.body.appendChild(this.dom)
}
syncState() {
this.dom.style.width = this.now + "%";
}
startTo(step, time) {
if (this.intervalCode !== 0) return;
this.intervalCode = setInterval(() => {
console.log("sss")
if (this.now + step > this.max) {
this.now = this.max;
this.syncState();
clearInterval(this.interval);
this.intervalCode = 0;
return;
}
this.now += step;
this.syncState()
}, time)
}
end() {
this.now = this.max;
clearInterval(this.intervalCode);
this.intervalCode = 0;
this.syncState();
}
}
let pb = new Progress(15, 0, 100, {parent : ".progress"});
//arg1 -> step length
//arg2 -> time(ms)
pb.startTo(5, 500);
//end to progress after 5s
setTimeout( () => {
pb.end()
}, 10000)
</script>

Answer 1

我认为核心问题是您复制的代码过于复杂，尤其是对初学者来说。我的建议是从你所知道的开始，不断积累。

以下是您希望只使用JavaScript和CSS的核心原理编写的功能。

let initialTime = 10; //All time in seconds
let timeLeft = initialTime;
let interval;
let progressBarTextElement = document.getElementById('progress-bar-text');
let progressBarElement = document.getElementById('progress-bar');
function render() {
let progressPercentage = (1 - (timeLeft / initialTime) ) * 100;

progressBarElement.style.width = progressPercentage + '%';
progressBarTextElement.innerHTML = timeLeft + 's';
}
function tick() {
timeLeft = timeLeft - 1;
if(timeLeft <= 0) {
clearInterval(interval); //Stops interval
}

render(); //Updates html
}
function startProgressBar() {
interval = setInterval(tick, 1000); //Will call tick every second
render();
}
startProgressBar();

html {font-family: -apple-system,BlinkMacSystemFont,"Segoe UI","Roboto","Oxygen","Ubuntu","Cantarell","Fira Sans","Droid Sans","Helvetica Neue",sans-serif;}
.progress-bar-continer {
height: 80px;
width: 100%;
position: relative;
display: flex;
justify-content: center;
align-items: center;
background-color: #406086;
}
.progress-bar {
background-color: #1b3e80;
position: absolute;
top: 0;
bottom: 0;
left: 0;
width: 0%;
transition: width 1s; /* Makes progressBar smooth */
transition-timing-function: linear; /* Try to remove this line for more tick tock feel */

}
.progress-bar-text {
color: white;
font-size: 24px;
font-weight: 700;
position: relative;
z-index: 1;
}

<div class="progress-bar-continer">
<div class="progress-bar" id="progress-bar"></div>
<div class="progress-bar-text" id="progress-bar-text"></div>
<div>

试着尽你所能理解代码，在上面添加任何你想要的功能都不会有问题。所有新奇的东西稍后都会有经验。