JS30 day28 - Video Speed Controller

作業內容

今天的作業是做出一個 bar 在影片旁邊，可以拉動調整影片速度，比較特別的是他是用純 div 做的而不是 input range 說實在這次的還滿簡單的，幾乎可以自己把它做完，自己在做的時候就只有卡在不知道怎麼顯示倍數的文字而已

學到什麼

• JS
  1. 要怎麼換算倍率跟百分比？ 首先拿到目前 mouse event 的高度，除以整個 bar 的高度得到百分比

  let startY = e.pageY - this.offsetTop
  const percent = startY / this.offsetHeight
  const height = Math.round(percent * 100) + '%'

  再來是自訂最大最小倍率乘以百分比

  const min = 0.4
  const max = 4
  const value = min + (max - min) * percent
  bar.textContent = `${value.toFixed(2)}x`

https://github.com/wesbos/JavaScript30

code 內容：

HTML:

<div class="wrapper">
  <video class="flex" width="765" height="430" src="http://clips.vorwaerts-gmbh.de/VfE_html5.mp4" loop controls></video>
  <div class="speed">
    <div class="speed-bar">1×</div>
  </div>
</div>

CSS:

body {
  margin: 0;
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
  background: #4C4C4C url('https://unsplash.it/1500/900?image=1021');
  background-size: cover;
  font-family: sans-serif;
}

.wrapper {
  width: 850px;
  display: flex;
}

video {
  box-shadow: 0 0 1px 3px rgba(0,0,0,0.1);
}

.speed {
  background: #efefef;
  flex: 1;
  display: flex;
  align-items: flex-start;
  margin: 10px;
  border-radius: 50px;
  box-shadow: 0 0 1px 3px rgba(0,0,0,0.1);
  overflow: hidden;
}

.speed-bar {
  width: 100%;
  background: linear-gradient(-170deg, #2376ae 0%, #c16ecf 100%);
  text-shadow: 1px 1px 0 rgba(0,0,0,0.2);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 2px;
  color: white;
  height: 16.3%;
}

JS:

const video = document.querySelector('.flex')
const bar = document.querySelector('.speed-bar')
const speed = document.querySelector('.speed')
let isDown = false

speed.addEventListener('mousemove', function(e){
  if(!isDown) return;
  let startY = e.pageY - this.offsetTop
  const percent = startY / this.offsetHeight
  const height = Math.round(percent * 100) + '%'
  bar.style.height = height

  const min = 0.4
  const max = 4
  const value = min + (max - min) * percent
  bar.textContent = `${value.toFixed(2)}x`
  video.playbackRate = value
})
speed.addEventListener('mousedown', ()=>{ isDown = true })
speed.addEventListener('mouseleave', ()=>{ isDown = false })
speed.addEventListener('mouseup', ()=>{ isDown = false })