Java Script Error Message Code
Contents |
References & Guides Learning web development Tutorials References Developer Guides Accessibility Game development ...more docs Mozilla Docs Add-ons Firefox javascript error object Developer ToolsFeedback Get Firefox help Get web development help Join the javascript error handling best practices MDN community Report a content problem Report a bug Search Search Languages Català (ca) Deutsch (de)
Javascript Try Without Catch
Español (es) Français (fr) Bahasa Indonesia (id) 日本語 (ja) 한국어 (ko) Polski (pl) Português (do Brasil) (pt-BR) Русский (ru) 中文 (简体) (zh-CN) 正體中文 (繁體) (zh-TW) Add a translation Edit
Throw Error Java
Advanced Advanced History Print this article MDN Web technology For developers JavaScript JavaScript reference Standard built-in objects Error Your Search Results ariyankhan josephmcasey AlexanderFradiani fscholz mondwan SphinxKnight janosch-x davidchase Mingun shawnacscott Sheppy ethertank Nickolay evilpie trevorh teoli davidbourguignon secoif DomenicDenicola dgchurchill timemachine3030 Sevenspade Potappo Sephr Brettz9 Mgjbot Allanbonadio Ptak82 JustinLudwig Error In This Article SyntaxParametersDescriptionError typesPropertiesMethodsError instancesPropertiesStandard javascript catch all errors propertiesVendor-specific extensionsMicrosoftMozillaMethodsExamplesThrowing a generic errorHandling a specific errorCustom Error TypesSpecificationsBrowser compatibilitySee also The Error constructor creates an error object. Instances of Error objects are thrown when runtime errors occur. The Error object can also be used as a base object for user-defined exceptions. See below for standard built-in error types. Syntax new Error([message[, fileName[, lineNumber]]]) Parameters message Optional. Human-readable description of the error. fileName Optional. The value for the fileName property on the created Error object. Defaults to the name of the file containing the code that called the Error() constructor. lineNumber Optional. The value for the lineNumber property on the created Error object. Defaults to the line number containing the Error() constructor invocation. Description Runtime errors result in new Error objects being created and thrown. This page documents the use of the Error object itself and its use as a constructor function. For a list of properties and methods inherited by Error instances, see Error.prototype. Error types Besides the generic Error constructor, there are six other core
as expected is a good start. Making your programs behave properly when encountering unexpected conditions is where it really
Javascript Error Message Popup
gets challenging. ¶ The problematic situations that a program can encounter define inaccuracy fall into two categories: Programmer mistakes and genuine problems. If someone forgets to pass a required argument to define miscalculation a function, that is an example of the first kind of problem. On the other hand, if a program asks the user to enter a name and it https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error gets back an empty string, that is something the programmer can not prevent. ¶ In general, one deals with programmer errors by finding and fixing them, and with genuine errors by having the code check for them and perform some suitable action to remedy them (for example, asking for the name again), or at least fail in http://eloquentjavascript.net/1st_edition/chapter5.html a well-defined and clean way. ¶ It is important to decide into which of these categories a certain problem falls. For example, consider our old power function:function power(base, exponent) { var result = 1; for (var count = 0; count < exponent; count++) result *= base; return result; } ¶ When some geek tries to call power("Rabbit", 4), that is quite obviously a programmer error, but how about power(9, 0.5)? The function can not handle fractional exponents, but, mathematically speaking, raising a number to the halfth power is perfectly reasonable (Math.pow can handle it). In situations where it is not entirely clear what kind of input a function accepts, it is often a good idea to explicitly state the kind of arguments that are acceptable in a comment. ¶ If a function encounters a problem that it can not solve itself, what should it do? In chapter 4 we wrote the function between:function between(string, start, end) { var startAt = string.indexOf(start) + start.length; var endAt = string.indexOf(end, startAt); return string.sli
users have encountered the annoying JavaScript error at some stage. This happens when a script in a web page contains an error or fails to execute correctly. Exactly what happens depends on the browser and type of error, but in most cases some sort of error notification will be displayed. The http://www.mediacollege.com/internet/javascript/basic/error.html Error Message In Internet Explorer's default setting, a small warning icon appears in the status bar like the one pictured left. Double-click this icon to display a window with the complete error message. The complete error message looks something http://www.javascriptkit.com/javatutors/trycatch2.shtml like this: Note: If you see a less detailed version of this window, click the "Show Details" button. You can choose to have this error window appear automatically whenever an error occurs. This could be annoying for general script error surfing, but it is very useful when writing your own JavaScript. This is because the error message always lets you know when something is wrong with your code, and even better, it usually tells you exactly where in the HTML document the problem lies (in the above example, line 71 character 1). What to Do When You See an Error If you are visiting a website which shows an error, you obviously can't fix it but script error message if you're feeling generous you might like to contact the webmaster and let them know. You can still view the page (disabling automatic error messages will make it easier), but whatever the script was supposed to do won't work. This may or may not effect on the functionality of the page. If you are the webmaster, you need to understand what the error message is telling you and fix it. Keep reading.... How to Fix JavaScript Errors There are two types of JavaScript error: Syntax Error: Occurs when there is a mistake in the way the code is written; for example, a typo or missing character. Runtime error: Occurs when the script is unable to complete its instructions; for example, if a specified object cannot be found. Syntax Error The function below contains an error and will result in the error message as pictured. In this case the message tells you that a closing parenthesis is missing. function showAlert() { alert('Hello World!'; } Not all error messages are as clear as this but once you've seen a few (and you will see a few!) you'll start to recognise what they mean. Runtime Error The function below is constructed correctly and will run with no problems as long as the variable something can be found (remember that a text string without quotes is assumed to be a variable).
As promised, we're going to take a closer look at the Error object that gets passed into the catch clause to see just what we can extract from it in an event of an error. The Error object in all browsers support the following two properties: name: The name of the error, or more specifically, the name of the constructor function the error belongs to. message: A description of the error, with this description varying depending on the browser. try{ document.body.filters[0].apply() } catch(e){ alert(e.name + "\n" + e.message) } Demo: Six possible values can be returned by the name property, which as mentioned correspond to the names of the error's constructors. They are: Error Name Description EvalError An error in the eval() function has occurred. RangeError Out of range number value has occurred. ReferenceError An illegal reference has occurred. SyntaxError A syntax error within code inside the eval() function has occurred. All other syntax errors are not caught by try/catch/finally, and will trigger the default browser error message associated with the error. To catch actual syntax errors, you may use the onerror event. TypeError An error in the expected variable type has occurred. URIError An error when encoding or decoding the URI has occurred (ie: when calling encodeURI()). This level of detail may be useful when you wish to sniff out a specific type of error in your catch clause. In the below, no DIV on the page exists with ID="mydiv". When trying to set its .innerHTML property, a TypeError occurs, since we're trying to assign the .innerHTML property to a null object: try{ document.getElementById("mydiv").innerHTML='Success' //assuming "mydiv" is undefined } catch(e){ if (e.name.toString() == "TypeError"){ //evals to true in this case //do something } } Ok, so maybe it's not that useful most of the time, but you just never know. Throwing your own errors (exce