仅从字符串中提取cookie的值

function extractCookieValue(cookieString, cookieName) {
  var cookies = cookieString.split("; ");
  for (var i = 0; i < cookies.length; i++) {
    var cookie = cookies[i].split("=");
    var key = cookie[0];
    var value = cookie[1];
    if (key === cookieName) {
      return value;
    }
  }
  return null;
}

// 示例用法
var cookieString = "name=John; age=30; token=abc123";
var cookieValue = extractCookieValue(cookieString, "token");
console.log(cookieValue); // 输出：abc123