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/*
JavaScript Bible, Fourth Edition
by Danny Goodman
John Wiley & Sons CopyRight 2001
*/
<HTML>
<HEAD>
<TITLE>Throwing a Custom Error Object Exception</TITLE>
<SCRIPT LANGUAGE="JavaScript">
var letters = new Array("A","B","C","D","E")
function getErrorObj(msg) {
var err = new Error(msg)
// take care of IE5/5.5
if (!err.message) {
err.message = msg
}
err.name = "MY_ERROR"
return err
}
function getLetter(fld) {
try {
var inp = parseInt(fld.value, 10)
if (isNaN(inp)) {
throw getErrorObj("Entry was not a number.")
}
if (inp < 1 || inp > 5) {
throw getErrorObj("Enter only 1 through 5.")
}
fld.form.output.value = letters[inp]
}
catch (e) {
switch (e.name) {
case "MY_ERROR" :
alert(e.message)
fld.form.output.value = ""
fld.focus()
fld.select()
break
default :
alert("Reload the page and try again.")
}
}
}
</SCRIPT>
</HEAD>
<BODY>
<H1>Throwing a Custom Error Object Exception</H1>
<HR>
<FORM>
Enter a number from 1 to 5:
<INPUT TYPE="text" NAME="input" SIZE=5>
<INPUT TYPE="button" VALUE="Get Letter" onClick=getLetter(this.form.input)>
Matching Letter is:<INPUT TYPE="text" NAME="output" SIZE=5>
</FORM>
</BODY>
</HTML>
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