如何返回字符串中某一个特定字符的个数

Question

<script>
  var a="ddddcdddcddsaf";
  function getNum(str,c){
return str.match(new RegExp("c","g")).length;
  }
  alert(getNum(a,"c"))
</script>

Answer 1

应该写成通用形式
<script>
  var a="ddddcdddcddsaf";
  function getNum(str,ch){
return str.match(new RegExp(ch,"g")).length;
  }
  alert(getNum(a,"c"))
</script>

Answer 2

<script>
  var a="ddddcdddcddsaf";
  function getNum(str,ch){
return (str.length-str.replace(ch,"").length);
  }
  alert(getNum(a,"c"))
</script>