<script language="javascript">
var strM = "javascript is a good script language";
//在此我想將字母a替換成字母A
alert(strM.replace("a","A"));

</script>
//結果，它只替換了首字母。但如果加上正則表達式結果就不一樣了！replace()支持正則表達式，它可以按照正則表達式的規則匹配字符或字符串，然后給予替換！
<script language="javascript">
var strM = "javascript is a good script language";
//在此我想將字母a替換成字母A
alert(strM.replace(/a/,"A"));
</script>
//但是結果還是沒有更改，稍加修改就OK了。

<script language="javascript">
var strM = "javascript is a good script language";
//在此將字母a全部替換成字母A,當正則表達式有"g"標志時，代表將處理整個字符串
alert(strM.replace(/a/g,"A"));
</script>