<script language="javascript">
var strM = "javascript is a good script language";
// Here I want to replace the letter a with the letter A
alert(("a","A"));
</script>
//So, it only replaces the initial letter. But if you add regular expressions, the result will be different! replace() supports regular expressions, which can match characters or strings according to the rules of regular expressions and then give a replacement!
<script language="javascript">
var strM = "javascript is a good script language";
// Here I want to replace the letter a with the letter A
alert((/a/,"A"));
</script>
//But the result still has not been changed, so it will be OK if you modify it slightly.
<script language="javascript">
var strM = "javascript is a good script language";
//Replace all letter a with letter A here. When the regular expression has the "g" flag, it means that the entire string will be processed.
alert((/a/g,"A"));
</script>