JavaScript DHTML/Development/Error Exceptions
Содержание
- 1 A Custom Object Exception
- 2 Throwing a Custom Error Object Exception
- 3 Catch that error!
- 4 <SCRIPT> function dosomething() { } function goodFunc(){ try { doSomething(); } catch (e) { if (e.description == "Object expected") { alert("Cannot find a function named doSomething!"); } else { alert ("Other error" + e.description); } } } </SCRIPT>
- 5 Throw that error!
- 6 Throwing an Error Object Exception
- 7 Throwing a String Exception
- 8 Handling Errors with onError
A Custom Object Exception
<source lang="html4strict">
/* 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>
Throwing a Custom Error Object Exception
<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>
</source>
An Exception Handling Example
<source lang="html4strict">
<HTML> <HEAD><TITLE>Exception Test</TITLE></HEAD> <SCRIPT LANGUAGE="JavaScript"></SCRIPT> <BODY>
This script only works with Internet Explorer 5, Navigator 6, or later browsers.
<SCRIPT LANGUAGE="JavaScript"></SCRIPT> </BODY> </HTML>
</source>
Catching an Error
<source lang="html4strict">
<HTML> <TITLE>Catch that error!</TITLE> <SCRIPT> function catchError(errString) {
try {
try {
if (errString == 42)
throw new Error (42, "errString is 42 !");
else
throw new Error (0, "errString is NOT 42 !");
}
catch(e) {
if (e.number == 42)
return (e.description + " Got this one!");
else
throw e; // re-throw the error
}
}
catch (e){
return(e.description + " This one not handled here!");
}
} </SCRIPT> </HEAD> <BODY>
Catch that error!
<FORM name="theForm">
| We can handle 42: | <INPUT type=text name=errText size=40 value="42"> | |
| <INPUT type=button name=btnThrow value="Catch it!" onClick="alert(catchError(document.theForm.errText.value));"> | ||
</FORM> </BODY> </HTML>
</source>
Catching the "Object Expected" Error
<source lang="html4strict">
<HTML> <BODY>
<SCRIPT> function dosomething() { } function goodFunc(){ try { doSomething(); } catch (e) { if (e.description == "Object expected") { alert("Cannot find a function named doSomething!"); } else { alert ("Other error" + e.description); } } } </SCRIPT>
<FORM> <INPUT type=button value="Click" onClick="goodFunc();"> </FORM> </BODY> </HTML>
</source>
Controlling Script Errors
<source lang="html4strict">
/* JavaScript Bible, Fourth Edition by Danny Goodman John Wiley & Sons CopyRight 2001
- /
<HTML> <TITLE>Error Dialog Control</TITLE> <SCRIPT LANGUAGE="JavaScript1.1"> // function with invalid variable value function goWrong() {
var x = fred
} // turn off error dialogs function errOff() {
window.onerror = doNothing
} // turn on error dialogs with hard reload function errOn() {
window.onerror = handleError
} // assign default error handler window.onerror = handleError // error handler when errors are turned off...prevents error dialog function doNothing() {return true} function handleError(msg, URL, lineNum) {
var errWind = window.open("","errors","HEIGHT=270,WIDTH=400")
var wintxt = "<HTML><BODY BGCOLOR=RED>"
wintxt += "An error has occurred on this page. "
wintxt += "Please report it to Tech Support."
wintxt += "<FORM METHOD=POST ENCTYPE="text/plain" "
wintxt += "ACTION=mailTo:support4@dannyg.ru >"
wintxt += "<TEXTAREA NAME="errMsg" COLS=45 ROWS=8 WRAP=VIRTUAL>"
wintxt += "Error: " + msg + "\n"
wintxt += "URL: " + URL + "\n"
wintxt += "Line: " + lineNum + "\n"
wintxt += "Client: " + navigator.userAgent + "\n"
wintxt += "-----------------------------------------\n"
wintxt += "Please describe what you were doing when the error occurred:"
wintxt += "</TEXTAREA>" wintxt += "<INPUT TYPE=SUBMIT VALUE="Send Error Report">" wintxt += "<INPUT TYPE=button VALUE="Close" onClick="self.close()">" wintxt += "</FORM></BODY></HTML>" errWind.document.write(wintxt) errWind.document.close() return true } </SCRIPT> </HEAD> <BODY> <FORM NAME="myform"> <INPUT TYPE="button" VALUE="Cause an Error" onClick="goWrong()"><P> <INPUT TYPE="button" VALUE="Turn Off Error Dialogs" onClick="errOff()"> <INPUT TYPE="button" VALUE="Turn On Error Dialogs" onClick="errOn()"> </FORM> </BODY> </HTML> </source>
<source lang="html4strict">
<HTML> <HEAD><TITLE>Exception Test</TITLE></HEAD> <SCRIPT LANGUAGE="JavaScript"></SCRIPT> <BODY> <SCRIPT LANGUAGE="JavaScript"></SCRIPT> </BODY> </HTML>
</source>
Throwing an Error
<source lang="html4strict">
<HTML> <HEAD> <TITLE>Throw that error!</TITLE> <SCRIPT> function throwError(errString) {
try {
throw new Error (42, errString);
}
catch(e){
alert("Error number: " + e.number + "; Description: " + e.description)
}
} </SCRIPT> </HEAD> <BODY>
Throw that error!
<FORM name="theForm">
| Enter text for the error: |
<INPUT type=text name=errText size=40> |
|
|
<INPUT type=button name=btnThrow value="Throw it!" onClick="throwError(document.theForm.errText.value);"> |
||
</FORM> </BODY> </HTML>
</source>
Throwing an Error Object Exception
<source lang="html4strict">
/* JavaScript Bible, Fourth Edition by Danny Goodman John Wiley & Sons CopyRight 2001
- /
<HTML> <HEAD> <TITLE>Throwing an 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
}
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) {
alert(e.message)
fld.form.output.value = ""
fld.focus()
fld.select()
}
} </SCRIPT> </HEAD> <BODY>
Throwing an Error Object Exception
<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>
</source>
Throwing String Exceptions
<source lang="html4strict">
<HTML> <HEAD> <TITLE>Throwing a String Exception</TITLE> <SCRIPT LANGUAGE="JavaScript"> var letters = new Array("A","B","C","D","E") function getLetter(fld) {
try {
var inp = parseInt(fld.value, 10)
if (isNaN(inp)) {
throw "Entry was not a number."
}
if (inp < 1 || inp > 5) {
throw "Enter only 1 through 5."
}
fld.form.output.value = letters[inp-1]
}
catch (e) {
alert(e)
fld.form.output.value = ""
fld.focus()
fld.select()
}
} </SCRIPT> </HEAD> <BODY>
Throwing a String Exception
<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>
</source>
Using the onError Event Handler
<source lang="html4strict">
<HTML> <HEAD> <TITLE>Handling Errors with onError</TITLE> <SCRIPT></SCRIPT> </HEAD> <BODY>
Handling Errors with onError
<FORM> <INPUT TYPE="BUTTON" ONCLICK="createAnError()" VALUE="Click here to generate an error."> </FORM> </BODY> </HTML>
</source>