使用javascrtip切换外部样式表，并使用本地存储进行保存

<link rel="stylesheet" href="styles.css" id="styleSheet">

function toggleStyle() {
  var styleSheet = document.getElementById("styleSheet");
  if (styleSheet.getAttribute("href") === "styles.css") {
    styleSheet.setAttribute("href", "alternate_styles.css");
  } else {
    styleSheet.setAttribute("href", "styles.css");
  }
}

<button onclick="toggleStyle()">切换样式</button>

function toggleStyle() {
  var styleSheet = document.getElementById("styleSheet");
  if (styleSheet.getAttribute("href") === "styles.css") {
    styleSheet.setAttribute("href", "alternate_styles.css");
    localStorage.setItem("style", "alternate_styles.css");
  } else {
    styleSheet.setAttribute("href", "styles.css");
    localStorage.setItem("style", "styles.css");
  }
}

// 在页面加载时检查本地存储中是否有样式选择，并应用该选择
window.onload = function() {
  var style = localStorage.getItem("style");
  var styleSheet = document.getElementById("styleSheet");
  if (style) {
    styleSheet.setAttribute("href", style);
  }
}