Raise Error Javascript
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中文 (简体) (zh-CN) Add a translation Edit Advanced Advanced History Print this article MDN Web technology For developers JavaScript JavaScript reference Statements and declarations throw Your Search Results Natalya_Surikova fscholz ptepper nacyot GuilhermeReda rxgx Dan-Dascalescu Havvy Ginden Sheppy tregagnon safjanowski Shiningtiti Mgjbot Ptak82 Maian Anonymous Dria throw In This javascript error handling best practices Article SyntaxDescriptionExamplesThrow an objectAnother example of throwing an objectRethrow an exceptionSpecificationsBrowser compatibilitySee also The throw statement throws a user-defined exception. Execution of the current function will stop (the statements after throw won't be executed), and control will be passed to the first catch block in the call stack. If no catch block exists among caller functions, the program will terminate. Syntax throw expression; expression The expression to throw. Description Use the throw statement to throw an exception. When you throw an exception, expression specifies the value of the exception. Each of the following throws an exception: throw "Error2"; // generates an exception with a string value throw 42; // generates an exception with the value 42 throw true; // generates an exception with the value true Also note that the throw statement is affected by automatic semicolon insertion (ASI) as no line terminator
the ability to create errors. My first reaction to the throw operator in Java was, "well that's stupid, why would you ever want to cause an error?" Errors were the enemy to me, something I sought to avoid, so no-throw-literal the ability to cause an error seemed like a useless and dangerous aspect of the language. javascript console error I thought it was dumb to include the same operator in JavaScript, a language that people just didn't understand in the first place. javascript rethrow Now with a great deal of experience under my belt, I'm a big fan of throwing my own errors. Doing so can lead to easier debugging and code maintenance when done properly. When programming, an error occurs when https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/throw something unexpected happens. Maybe the incorrect value was passed into a function or a mathematical operation had an invalid operand. Programming languages define a base set of rules that, when deviated from, result in errors so that the developer can fix the code. Debugging would be nearly impossible if errors weren't thrown and reported back to you. If everything failed silently, it would take you a long time to notice that there was an issue in https://www.nczonline.net/blog/2009/03/03/the-art-of-throwing-javascript-errors/ the first place, let alone isolate and fix it. Errors are the friends of developers, not enemies. The problem with errors is that they tend to pop up in unexpected places and at unexpected times. To make matters worse, the default error messages are usually too terse to really explain what went wrong. JavaScript error messages are notoriously uninformative and cryptic (especially in Internet Explorer), which only compounds the problem. Imagine if an error popped up with a message that said, "this function failed because this happened." Instantly, your debugging task becomes easier. This is the advantage of throwing your own errors. It helps to think of errors as built-in failure cases. It's always easier to plan for a failure at a particular point in code than it is to anticipate failure everywhere. This is a very common practice in product design, not just in code. Cars are built with crumple zones, areas of the frame that are designed to collapse in a predictable way when impacted. Knowing how the frame will react in a crash, which parts will fail, allow the manufacturers to ensure passenger safety. Your code can be constructed in the same way. Even though JavaScript has come a long way in the past few years, JavaScript developers still have far less tools to aid in debugging than developers of other languages. Throwing errors in
here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and policies of this http://stackoverflow.com/questions/783818/how-do-i-create-a-custom-error-in-javascript site About Us Learn more about Stack Overflow the company Business Learn more about hiring developers or posting ads with us Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 6.2 million programmers, just like you, helping each other. Join them; it only takes a minute: Sign up How do error java I create a custom Error in JavaScript? up vote 134 down vote favorite 57 For some reason it looks like constructor delegation doesn't work in the following snippet: function NotImplementedError() { Error.apply(this, arguments); } NotImplementedError.prototype = new Error(); var nie = new NotImplementedError("some message"); console.log("The message is: '"+nie.message+"'") Running this gives The message is: ''. Any ideas as to why, or if there is a raise error javascript better way to create a new Error subclass? Is there a problem with applying to the native Error constructor that I don't know about? javascript exception share|improve this question edited Jul 26 '13 at 21:01 B T 14.9k1397125 asked Apr 23 '09 at 22:35 cdleary 27.4k40130178 Does nie instanceof NotImplementedError assertion work after your changes? I thought that in order for this to work you need to define NotImplementedError.prototype.constructor explicitly. –jayarjo Jul 9 '11 at 9:45 Next time, please tear out all the extraneous code that isn't required to demonstrate your issue. Also, wtc is js.jar ? Is that needed to reproduce the problem? –B T Jul 26 '13 at 20:39 2 Edited this question so that its understandable in 10 seconds rather than 10 minutes –B T Jul 26 '13 at 20:46 I created an inheritance/class library that inherits from Error types properly: github.com/fresheneesz/proto –B T Sep 10 '13 at 17:33 1 jsfiddle for a few of the top answers. –Nate Sep 22 '15 at 13:56 | show 1 more comment 17 Answers 17 active oldest votes up vote 127 down vot