Error object constructorS2C Home « Globals « Error

In JavaScript you create an error instance using the constructor Error.

Description

Creates a generic Error object, this is created by JavaScript automatically when runtime errors are encountered.

Syntax

Parameters

Class Properties

Instance Properties

Class Methods

None.

Instance Methods

By using methods of the Error object we can also access elements of errors, manipulate errors after creation and even create new errors from existing errors.

Examples

Let's look at some examples of throwing an error within our code.

// Throw an error.
try {
  throw new Error();
} catch (e) {
    alert('An error: ' + e.name);
}  
// Throw an error with a message.
try {
  throw new Error('Throwing an error.');
} catch (e) {
    alert('An error with message: ' + e.name + ': ' + e.message);
}  

We can also create our own Error instances as the example below shows.

// Create our own Error object.
function ourError(message) {  
  this.name = 'OurError';  
  this.message = message || 'Default Message Used When No Message Passed';
}   
// Inherit from the Error prototype.
ourError.prototype = new Error();  
ourError.prototype.constructor = ourError;   
// Throw an error.
try {  
  throw new ourError();  
} catch (e) {  
  alert('Our Error: ' + e.name + ' Message: ' + e.message);
}   
// Throw an error and a message.
try {  
  throw new ourError('A Message we have passed');  
} catch (e) {  
  alert('Our Error: ' + e.name + ' Our Message: ' + e.message);
} finally {  
  alert('A finally statement will always be executed!');
}   

Related Tutorials

JavaScript Advanced Tutorials - Lesson 2 - Errors

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