Javascript: 你如何使用多个 if else 语句来引用不同的元素？

Question

我是 JavaScript 的新手，所以这可能非常明显，但我正在尝试使用红绿灯构建 Andon 系统，如果数字高于或低于某个数字，灯会改变颜色（即 > 5 = 绿色）。总共有九组灯，我已经成功地通过使用查询 select all 然后更改不透明度来根据变量更改了一组灯。

当我尝试使用第二盏灯执行此操作时，没有任何反应。我试图通过在 html 和 CSS 中以不同方式命名我的 div 元素来使其工作，例如"Zcircle"、"A1circle"

Link来码笔。

任何帮助将不胜感激！谢谢

代码

HTML:

div class="Zcontainer">
       <div class="Zcircle red" color="red">
       </div>
       <div class="Zcircle yellow" color="yellow"></div>
       <div class="Zcircle green" color="green"></div>
     </div>

     <div class="A1container">
       <div class="A1Circle red" color="red">
       </div>
       <div class="A1Circle yellow" color="yellow"></div>
       <div class="A1Circle green" color="green"></div>
     </div>

CSS


.Zcontainer {
  background-color: #2c3e50;
  border-radius: 60px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: space-around;
  position: relative;
  left: 250px;
  bottom: 75px;
  padding: 15px 0;
  height: 200px;
  width: 70px;
}

.Zcircle {
  background-color: rgba(0, 0, 0, 0.3);
  border-radius: 100%;
  position: relative;
  height: 40px;
  width: 40px;
}

.Zcircle::after {
  border-right: 4px solid rgba(255, 255, 255, 0.6);
  border-radius: 100%;
  content: " ";
  position: absolute;
  top: 5px;
  left: 0px;
  width: 30px;
  height: 30px;
}

.Zcircle.red {
  background-color: #c0392b;
  box-shadow: 0 0 20px 5px #c0392b;
}

.Zcircle.yellow {
  background-color: #f1c40f;
  box-shadow: 0 0 20px 5px #f1c40f;
}

.Zcircle.green {
  background-color: #2ecc71;
  box-shadow: 0 0 20px 5px #2ecc71;
}

.A1container {
  background-color: #2c3e50;
  border-radius: 60px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: space-around;
  position: relative;
  left: 350px;
  bottom: 275px;
  padding: 15px 0;
  height: 200px;
  width: 70px;
}

.A1circle {
  background-color: rgba(0, 0, 0, 0.3);
  border-radius: 100%;
  position: relative;
  height: 40px;
  width: 40px;
}

.A1circle::after {
  border-right: 4px solid rgba(255, 255, 255, 0.6);
  border-radius: 100%;
  content: " ";
  position: absolute;
  top: 5px;
  left: 0px;
  width: 30px;
  height: 30px;
}

.A1circle.red {
  background-color: #c0392b;
  box-shadow: 0 0 20px 5px #c0392b;
}

.A1circle.yellow {
  background-color: #f1c40f;
  box-shadow: 0 0 20px 5px #f1c40f;
}

.A1circle.green {
  background-color: #2ecc71;
  box-shadow: 0 0 20px 5px #2ecc71;
}

Javascript

//first traffic light - this one works

var myElements = document.querySelectorAll(".Zcircle");

for (var i = 0; i < myElements.length; i++) {
  myElements[i].style.opacity = 0;
}

var a = 2 //value which will make the light change color

if (a > 4) {
  var myElements = document.querySelectorAll(".Zcircle");

  for (var x = 2; x < myElements.length; i++) {
    myElements[x].style.opacity = 1;
  }
} else if (a < 3) {
  var myElements = document.querySelectorAll(".Zcircle");

  for (var x = 0; x < myElements.length; i++) {
    myElements[x].style.opacity = 1;
  }
} else {
  var myElements = document.querySelectorAll(".Zcircle");

  for (var x = 1; x < myElements.length; i++) {
    myElements[x].style.opacity = 1;
  }
}

//second traffic light - this one doesnt work

var myElements = document.querySelectorAll(".A1circle");

for (var a = 0; a < myElements.length; a++) {
  myElements[a].style.opacity = 0;
}

var b = 1; //value which will make the light change color 

if (b > 4) {
  var myElements = document.querySelectorAll(".A1circle");

  for (var b = 2; x < myElements.length; b++) {
    myElements[b].style.opacity = 1;
  }
} else if (b < 3) {
  var myElements = document.querySelectorAll(".A1circle");

  for (var b = 0; b < myElements.length; b++) {
    myElements[b].style.opacity = 1;
  }
} else {
  var myElements = document.querySelectorAll(".A1circle");

  for (var b = 1; b < myElements.length; b++) {
    myElements[b].style.opacity = 1;
  }
}

Answer 1

这是您想要的最终代码。

let allZCircles = select(".Zcircle"),
    allA1Circles = select(".A1Circle"),
    items = 2;

//hides all the lights
setOpacity(allZCircles, 0);
setOpacity(allA1Circles, 0);

//as per op's requirnments
if(items >= 5) {
    setOpacity(select(".Zcircle.green"), 1);  // makes green light visible
    setOpacity(select(".A1Circle.green"), 1);  // makes green light visible
} else if (items < 3) {
    setOpacity(select(".Zcircle.red"), 1);  // makes red light visible
    setOpacity(select(".A1Circle.red"), 1);  // makes red light visible
} else {
    setOpacity(select(".Zcircle.yellow"), 1);  // makes yellow light visible
    setOpacity(select(".A1Circle.yellow"), 1);  // makes yellow light visible
}


function select(selector) {return document.querySelectorAll(selector); }
function setOpacity(selectors, opacity) {selectors.forEach((selector) => selector.style.opacity = opacity);}

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