24.74. Error: a generic exception ECMAScript v3: Object  Error 24.74.1. Constructor new Error( )
new Error(message) 24.74.1.1. Arguments
message An optional error message that provides details about the exception. 24.74.1.2. Returns A newly constructed Error object. If the message argument is specified, the Error object uses it as the value of its message property; otherwise, it uses an implementation-defined default string as the value of that property. When the Error( ) constructor is called as a function, without the new operator, it behaves just as it does when called with the new operator. 24.74.2. Properties
message An error message that provides details about the exception. This property holds the string passed to the constructor or an implementation-defined default string.
name A string that specifies the type of the exception. For instances of the Error class and all of its subclasses, this property specifies the name of the constructor used to create the instance. 24.74.3. Methods
toString( ) Returns an implementation-defined string that represents this Error object. 24.74.4. Description Instances of the Error class represent errors or exceptions and are typically used with the throw and try/catch statements. The name property specifies the type of the exception, and the message property can provide human-readable details about the exception. The JavaScript interpreter never throws Error objects directly; instead, it throws instances of one of the Error subclasses, such as SyntaxError or RangeError. In your own code, you may find it convenient to throw Error objects to signal exceptions, or you may prefer to simply throw an error message or error code as a primitive string or number value. Note that the ECMAScript specification defines a toString( ) method for the Error class (it is inherited by each of the subclasses of Error) but that it does not require this toString( ) method to return a string that contains the contents of the message property. Therefore, you should not expect the toString( ) method to convert an Error object to a meaningful, human-readable string. To display an error message to a user, you should explicitly use the name and message properties of the Error object. 24.74.5. Examples You might signal an exception with code like the following: function factorial(x) { if (x < 0) throw new Error("factorial: x must be >= 0"); if (x <= 1) return 1; else return x * factorial(x-1); }
And if you catch an exception, you might display its to the user with code like the following (which uses the client-side Window.alert( ) method): try { &*(&/* an error is thrown here */ } catch(e) { if (e instanceof Error) { // Is it an instance of Error or a subclass? alert(e.name + ": " + e.message); } }
24.74.6. See Also EvalError, RangeError, ReferenceError, SyntaxError, TypeError, URIError | 