function checkForm() {
var u = document.form_name.check.value;
var s = /^[-a-zA-Z0-9_]+(/.[-a-zA-Z0-9_]+)*@[-a-zA-Z0-9_]+(/.[-a-zA-Z0-9_]+)*$/;
var a = s.exec(u);
var a = s.test(u);
var a = u.match(s);
var a = u.search(s);
alert(a);
}

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

<script type="text/javascript">
var str="How are you doing today?"
document.write(str.split(" ") + "<br />")
document.write(str.split("") + "<br />")
document.write(str.split(" ",3))
</script>