This article is about javascript and its error and exception HANDLING.
Let us first know what javascript exactly is before going into its errors and exception HANDLING.
The original purpose of JavaScript was to “bring online pages alive.”
Scripts are what this language refers to as programmes. They can be included directly in the HTML of a web page and executed automatically when the page loads.
Plain text is used to deliver and run scripts. They don’t require any further setup or compilation to function.
JavaScript and Java are significantly different from one another in this regard.
Today, JavaScript can run on any device that has a specialised application called the JavaScript engine, including servers, browsers, and other devices.
An embedded engine in the browser is sometimes referred to as a “JavaScript virtual machine.”
Javascript Errors:
Javascript errors can be divided into three categories: logical, runtime, and syntax problems.
SYNTAX ERROR:
In traditional programming languages like C and C++, syntax errors—also known as parsing errors—occur at compile time. In JavaScript, they happen at interpret time.
For instance, the lack of a closing parenthesis in the line after it results in a syntactic mistake.
When a syntax error occurs in JavaScript, it only affects the code that is part of the same thread as the error. The remaining code in other threads continues to run as long as it doesn’t depend on the code that contains the syntax error.
RUNTIME ERRORS:
Runtime errors, also known as exceptions, happen when a programme is being executed (after compilation and interpretation).
The thread in which an exception occurs is also affected, allowing other JavaScript threads to carry on with their regular operations.
LOGICAL ERRORS:
One of the most challenging types of errors to find is logical ones. These mistakes are not due to runtime or syntactic faults. Instead, they happen when you make a logical error in your script and do not get the desired outcome because the type of logic you wish to include in your application depends on your business requirements, you cannot notice those problems.
Try and attempt to catch… Lastly, the try statement creates a code block that will execute (to try).
A code block is defined by the catch statement to address any errors.
The finally clause specifies a code block that will execute regardless of the outcome.
A unique error is defined by the try statement.
There Will Be Mistakes!
Various issues can arise when running JavaScript code.
Faults can be caused by incorrect input, programming errors, or other unforeseen circumstances.
Despite the fact that Error is a generic function Object() { [native code] }, it is accompanied by the following commonly used error kinds or constructors:
EvalError: This global function, which is used to evaluate the js string code, produces an instance for the error that occurred in eval().
When the js engine raises an internal error, InternalError creates an instance.
When a numeric variable or parameter is outside of its permitted range, an error called RangeError is generated.
When an invalid reference is de-referenced, an instance of the error known as ReferenceError is created.
SyntaxError: When parsing the eval, a possible syntax error instance is formed ().
An instance is created for a variable when it is not a valid type, resulting in a type error.
EXCEPTIONS HANDLING IN JAVASCRIPT:
An exception denotes the existence of an abnormal state that calls for specialised operating methods. An exception in programming is a piece of code that deviates from the standard design and causes problems. Such exceptions need to be handled using specialist programming techniques.
How to handle exceptions:
The process or method of handling aberrant statements in the code and carrying them out in programming is known as exception handling. Additionally, it makes it possible to control how the code or programme flows. Several handlers are used to handle the code, which process the exception and run the code.
Exception management:
To raise an exception, use a throw statement. It implies that a throw exception is raised if an exceptional circumstance arises.
The try…catch block is used to handle the exception that was thrown. Runtime errors are errors that occur during runtime. Exceptions are the programmes that produce runtime errors. Therefore, runtime faults are handled by exception handlers.
A logical error is when there is a programming error that prevents the programme from producing the desired results or from terminating properly. A logical error is one such error.
Problem Object
An Error object is created and thrown whenever a runtime error occurs. Such a thing can serve as a base.
A try…catch statement is a standard construct in many computer languages. In essence, it is utilised to manage the code’s prone to errors. It first checks the code for any flaws it might have, then it takes steps to fix any errors (if occur). The try…catch statements are a wonderful place to hold complex code when programming.
Let’s talk about each individual statement block separately:
The code that has to be tested for any errors is preserved inside the try block in this case. If a mistake occurs, control is sent to the catch block, which takes the appropriate steps to handle it. If not, it runs the code that is written there.
Catch-all statement: This block executes a series of statements to deal with any errors that may have occurred in the code. Either the built-in handler or the user-defined exception handler is present in this block. Only when error-prone code needs to be handled in the try block does this block go into action. The catch block is skipped in any other case.
Please take note that the catch statement only runs after the try statement. A try block may also include one or more catch blocks.
Try…catch…finally statements:
Try and catch statements are run first, followed by an optional block of instructions called finally. The exception cannot be thrown if the finally block is not holding. Whether or whether an exception is thrown, any finally block code that is present will undoubtedly be executed. It is unconcerned with the results as well.
