Javascript Create New Error
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Javascript Custom Error Es6
declarations throw Your Search Results fscholz ptepper nacyot GuilhermeReda rxgx Dan-Dascalescu Havvy Ginden Sheppy tregagnon safjanowski Shiningtiti Mgjbot Ptak82 Maian Anonymous Dria throw In This 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 javascript extend error 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 between the throw keyword and the expression is allowed. Examples Throw an object You can specify an object when you throw an exception. You can then reference the object's properties in the catch block. The following example creates an object of type UserException and uses it in a throw statement. function UserException(message) { this.message = message; this.name = "UserException"; } function getMonthName(mo) { mo = mo-1; // Adjust month nu
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Es6 Extend Error
Join them; it only takes a minute: Sign up How do 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: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/throw 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 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 14.9k1397124 asked Apr 23 http://stackoverflow.com/questions/783818/how-do-i-create-a-custom-error-in-javascript '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 vote accepted Update your code to assign your prototype to the Error.prototype and the instanceof and your asserts work. function NotImplementedError(message) { this.name = "NotImplementedError"; this.message = (message || ""); } NotImplementedError.prototype = Error.prototype; However, I would just throw your own object and just check the name property. throw {name : "NotImplementedError", message : "too lazy to implement"}; Edit based on comments After looking at the comments and trying to remember why I would assign prototype to Error.prototype instead of new Error() like N
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 http://www.javascriptkit.com/javatutors/trycatch2.shtml 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" custom error + 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 javascript custom error 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 (exceptions) Instead of waiting for one of the 6 types of errors above to occur before control is automatically transferre