JavaScript Tutorials - Herong's Tutorial Examples - 2.33, by Herong Yang
The "Error" Object Type - Runtime Exceptions
This section provides a quick description and a tutorial example script on the 'Error' built-in object type, which is used to create 'Error' objects for runtime exception handling.
The "Error" object type is a built-in object type to be used to create a "Error" object, representing a runtime exception. It has the following main features:
Here is a tutorial example script showing some of those features:
// Error_Object_Type.js // Copyright (c) 2013 HerongYang.com. All Rights Reserved. // Creating a new Error object var myObject = new Error("Too many users on herongyang.com"); // Checking this object println("\nAbout this \"myObject\":"); println(" Type = "+(typeof myObject)); println(" Instance Of Object: "+(myObject instanceof Object)); println(" Instance Of Error: "+(myObject instanceof Error)); // Throw my dummy error and catch it try { // If # sessions on site > 100 throw myObject; } catch (myError) { println("\nAbout this \"myError\":"); println(" Type = "+(typeof myError)); println(" Instance Of Error: "+(myError instanceof Error)); println(" myError.name: "+myError.name); println(" myError.message: "+myError.message); } // Catch a real error try { var o = null; o.toString(); } catch (realError) { println("\nAbout this \"realError\":"); println(" Type = "+(typeof realError)); println(" Instance Of Error: "+(realError instanceof Error)); println(" realError.name: "+realError.name); println(" realError.message: "+realError.message); }
If you run this script with "jrunscript", you will get:
About this "myObject": Type = object Instance Of Object: true Instance Of Error: true About this "myError": Type = object Instance Of Error: true myError.name: Error myError.message: Too many users on herongyang.com About this "realError": Type = object Instance Of Error: true realError.name: TypeError realError.message: Cannot call method "toString" of null
Now we know how to create "Error" objects with the "Error()" constructor.
Read other "Error" related chapters to see more tutorial examples.
Table of Contents
ECMAScript Language Specification and JavaScript Dialects
Data Types, Variables and Expressions
Creating, Accessing, and Manipulating Arrays
Defining and Calling Functions
Web Browser Supporting JavaScript
Server-Side and Client-Side Web Scripting
Defining Your Own Object Types
Inheritance of Properties and Methods through the Prototype Object Chain
'jrunscript' - JavaScript Shell Command from JDK
Using Functions as "Function" Objects
►Introduction to Built-in Object Types
Overview of Built-in Object Types
The "Object" Object Type - The Root Object Type
The "Global" Object Type - The Invisible Global Container
Global Properties and Functions Defined in ECMAScript
Global Properties and Functions Provided by "jrunscript"
The "Function" Object Type - Functions Are Objects
The "Array" Object Type - Arrays Are Objects
The "JSON" Object Type - parse() and stringify()
The "String" Object Type - Not Equal to String Primitive Type
The "Boolean" Object Type - Wrapping Boolean Values into Objects
The "Number" Object Type - Not Equal to Number Primitive Type
The "Date" Object Type - Managing Dates and Times
The "RegExp" Object Type - Regular Expression Patterns
►The "Error" Object Type - Runtime Exceptions
The "Math" Object Type - The Math Container
W3C's Document Object Model (DOM) Specifications