使用按钮删除和添加类

Question

我尝试使用按钮删除课程.computer-off并添加.computer-on，反之亦然。我尝试了很多方法，但无济于事。这是一种方法：

HTML ：

<div id="computer-screen" class="computer-off">

    <button onclick="computerPower()" class="power-button">Power</button>

</div>

JS ：

function computerPower() {
    if ( $("#computer-screen").hasClass('computer-off') ) {
        document.getElementById('computer-screen').removeClass('computer-off').addClass('computer-on');
    } else {
        document.getElementById("computer-screen").removeClass('computer-on').addClass('computer-off');
    }
};

Answer 1

我建议，鉴于你出现（试图）使用jQuery：

$('#power').on('click', function() {
  $('#computer-screen').toggleClass('computer-off computer-on');
});

$('#power').on('click', function() {
  $('#computer-screen').toggleClass('computer-off computer-on');
});

#computer {
  width: 60%;
  margin: 1em auto;
  padding: 1em;
  border: 1px solid darkgrey;
  overflow: hidden;
  border-radius: 0.4em 0.4em 0 0;
}
#computer-screen {
  border-radius: 0.5em;
  height: 15em;
}
.computer-off {
  background-color: #000;
}
.computer-on {
  background-color: #060;
  box-shadow: 0 0 1.0em #060;
}
#power {
  cursor: pointer;
  position: relative;
  float: right;
  width: 2em;
  height: 2em;
  line-height: 2em;
  border-radius: 50%;
  border: 1px solid #aaa;
  margin-top: 0.3em;
}
.computer-on + #power {
  box-shadow: inset 0 1px 3px #666;
}
#power::before {
  content: '';
  position: absolute;
  top: 0.3em;
  bottom: 0.75em;
  left: 0.9em;
  right: 0.9em;
  background-color: #ccc;
}
#power::after {
  content: '';
  height: 1em;
  width: 1em;
  position: absolute;
  border: 0.2em solid #ccc;
  border-top-color: transparent;
  border-radius: 50%;
  bottom: 0.3em;
  left: 0.3em;
}
#computer-screen.computer-on + #power::before {
  background-color: #0f0;
}
#computer-screen.computer-on + #power::after {
  border-color: #0f0;
  border-top-color: transparent;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id="computer">
  <div id="computer-screen" class="computer-off"></div>
  <div id="power"></div>
</div>

或者，在纯JavaScript中：

document.getElementById('power').addEventListener('click', function() {
  var screen = document.getElementById('computer-screen');
  screen.classList.toggle('computer-off');
  screen.classList.toggle('computer-on');
});

document.getElementById('power').addEventListener('click', function() {
  var screen = document.getElementById('computer-screen');
  screen.classList.toggle('computer-off');
  screen.classList.toggle('computer-on');
});

#computer {
  width: 60%;
  margin: 1em auto;
  padding: 1em;
  border: 1px solid darkgrey;
  overflow: hidden;
  border-radius: 0.4em 0.4em 0 0;
}
#computer-screen {
  border-radius: 0.5em;
  height: 15em;
}
.computer-off {
  background-color: #000;
}
.computer-on {
  background-color: #060;
  box-shadow: 0 0 1.0em #060;
}
#power {
  cursor: pointer;
  position: relative;
  float: right;
  width: 2em;
  height: 2em;
  line-height: 2em;
  border-radius: 50%;
  border: 1px solid #aaa;
  margin-top: 0.3em;
}
.computer-on + #power {
  box-shadow: inset 0 1px 3px #666;
}
#power::before {
  content: '';
  position: absolute;
  top: 0.3em;
  bottom: 0.75em;
  left: 0.9em;
  right: 0.9em;
  background-color: #ccc;
}
#power::after {
  content: '';
  height: 1em;
  width: 1em;
  position: absolute;
  border: 0.2em solid #ccc;
  border-top-color: transparent;
  border-radius: 50%;
  bottom: 0.3em;
  left: 0.3em;
}
#computer-screen.computer-on + #power::before {
  background-color: #0f0;
}
#computer-screen.computer-on + #power::after {
  border-color: #0f0;
  border-top-color: transparent;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id="computer">
  <div id="computer-screen" class="computer-off"></div>
  <div id="power"></div>
</div>

参考文献：

• JavaScript的：
  • document.querySelector()。
  • Element.classList。
• jQuery的：
  • toggleClass()。