小编Lar*_*mia的帖子

const getPlaceholderColor = () => {
  let inputEl = document.querySelector('.myClass');
  let inputElStyle = window.getComputedStyle(inputEl, '::placeholder');
  
  let resultTarget = document.getElementById('colorResult');
  let placeholderColor = inputElStyle.getPropertyValue('color');
  resultTarget.innerHTML = `Placeholder color: ${placeholderColor}`;
}

.myClass::placeholder {
  color: #004085;
}

.marginTop20 {
  margin-top: 20px;
}

<input
  type="text"
  placeholder="Enter name"
  class="myClass"
/>

<button onClick="getPlaceholderColor()">Get placeholder color</button>

<div class="marginTop20" id="colorResult"></div>