检索字符串中 "Mifengjc" 的子串

<p>搜索字符串 "Mifengjc", 并显示匹配的起始位置：</p>

<button onclick="myFunction()">点我</button>

<p id="demo"></p>

<script>

  function myFunction() {

    var str = "Visit Mifengjc!";

    var n = str.search("Mifengjc");

    document.getElementById("demo").innerHTML = n;

  }

</script>