如何在字符串中仅在某个锚点之后进行替换？

function replaceAfterAnchor(str, anchor, replacement) {
  // 查找锚点的位置
  var anchorIndex = str.indexOf(anchor);
  
  // 如果找到了锚点
  if (anchorIndex !== -1) {
    // 分割字符串为锚点之前和之后的部分
    var beforeAnchor = str.slice(0, anchorIndex + anchor.length);
    var afterAnchor = str.slice(anchorIndex + anchor.length);
    
    // 替换锚点之后的部分
    var replacedAfterAnchor = afterAnchor.replace(/./g, replacement);
    
    // 拼接锚点之前和替换后的部分
    return beforeAnchor + replacedAfterAnchor;
  }
  
  // 如果未找到锚点，则返回原始字符串
  return str;
}

// 示例用法
var originalString = "Hello, world! This is a test.";
var anchor = "world";
var replacement = "*";
var replacedString = replaceAfterAnchor(originalString, anchor, replacement);
console.log(replacedString);