Uses of the finally statement

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This is a very basic question. In Java I use the finally statement to close resources because "it's a good practice". I've been developing in Javascript and then in Node.js during some years and I've never used the finally statement. I know that in Node.js all of us follow the first parameter error handling pattern. Anyway, the 2 following snippets do the same:

try{
    throw 123
}catch (e){

}finally{
    console.log(1)
}

.

try{
    throw 123
}catch (e){

}

console.log(1)

Both print 1.

Why is finally a keyword if it has no real benefit? The clean up code can be put inside the catch.

finally is useful for more than just exception handling — it allows the programmer to avoid having cleanup code accidentally bypassed by a return, continue, or break.

Just a simple and straightforward example that shows the difference. There is a return that breaks the function completion, but the console.log in finally is called while the last console.log is skipped.

let letsTry = () => {

  try {
    // there is a SyntaxError
    eval('alert("Hello world)');
    
  } catch(error) {
    console.error(error);
	
    // break the function completion
    return;
  } finally {
      console.log('finally')
  }

  // This line will never get executed
  console.log('after try catch')
}

letsTry();

The finally Block (The Java™ Tutorials > Essential Classes , of improvements introduced in later releases and might use technology no longer available. The finally block always executes when the try block exits. But finally is useful for more than just exception handling — it allows the programmer  By using a finally block, you can clean up any resources that are allocated in a try block, and you can run code even if an exception occurs in the try block. Typically, the statements of a finally block run when control leaves a try statement.

But try this:

try {
    throw "foo"
} catch (e) {
    throw "bar"
} finally {
    console.log("baz")
}

console.log("quux")

If a second error is thrown from within the catch block, the code after the try...catch block will not run. The finally block will always run, even if there is an error in the catch block.

Furthermore, the finally block runs even if a return or break statement stops the code in the try or catch block. return statements in the finally block override return statements in the try or catch block.

function foo() {
    try {
        return "bar";
    } finally {
        return "baz";
    }
}

foo() // "baz"

Java Finally block - Exception handling, close() statement is used to close all the open streams in a program. Its a good practice to use close() inside finally block. Since finally block executes even if  The finally block always executes when the try block exits. This ensures that the finally block is executed even if an unexpected exception occurs. But finally is useful for more than just exception handling — it allows the programmer to avoid having cleanup code accidentally bypassed by a return, continue, or break.

oracle docs provide a good answer to this. Bottom line: finally gets called always! Even when you catch only one kind of exception (not the global catch), then finally gets called (after which your application probably breaks if there is no other catch)

Java Finally block, Finally block in java can be used to put "cleanup" code such as closing a file, closing connection etc. Usage of Java finally. Let's see the different cases where java  An iterator uses a Yield statement to return each element of the collection one at a time. You call an iterator function by using a For EachNext Statement. A Yield statement can be inside a Try block. A Try block that contains a Yield statement can have Catch blocks, and can have a Finally block.

the finally block is meant for a special purpose.

finally is useful for more than just exception handling — it allows the programmer to avoid having cleanup code accidentally bypassed by a return, continue, or break. Putting cleanup code in a finally block is always a good practice, even when no exceptions are anticipated.

Since it wont effect your business logic,Still it's compiler friendly,In memory aspects.

TryCatchFinally statement, Learn to use exception handling with Visual Basic Try/Catch/Finally statements. The try-finally statement is especially useful for routines that have several places where a check is made for an error that could cause premature return from the routine. For related information and a code sample, see try-except Statement .

This is a very good question.

There is little to no reason to use finally in javascript, but I can imagine situations where it could be of practical use.

Suppose you have a webpage where you show a certain div after some user action, e.g. button clicked. The div shows some logging for instance for the action the user requested. After the action is complete (error or no error), you want to be sure to hide the div again. For that you can use the finally clause.

function doSomething() {
    var d = document.getElementById("log");
    show(d);
    try {
        ... execute action ...
    } catch(e) {
        log(e);
    } finally {
        hide(d);
    }
}

In general, as you mentioned, exceptions are less and less used in JavaScript in favor of error callbacks. So, one could as well ask, what good uses are for exceptions in JavaScript in general.

try-finally Statement, The try-finally statement is a Microsoft extension to the C and C++ languages that enables target applications to guarantee execution of  The try statement in Python can have an optional finally clause. This clause is executed no matter what, and is generally used to release external resources. This clause is executed no matter what, and is generally used to release external resources.

C#, The finally block does not contain any return, continue, break statements because it does not allow controls to leave the finally block. You can also use finally block  A Try statement can include multiple Catch blocks for different kinds of errors. A Finally block can be used to free any resources that are no longer needed by your script. Try, Catch, and Finally resemble the Try, Catch, and Finally keywords used in the C# programming language.

Python finally Keyword, Definition and Usage. The finally keyword is used in tryexcept blocks. It defines a block of code to run when the tryexceptelse block is final. The finally block  Java finally block is a block that is used to execute important code such as closing connection, stream etc. Java finally block is always executed whether exception is handled or not. Java finally block follows try or catch block. Note: If you don't handle exception, before terminating the program, JVM executes finally block(if any). Why use java finally

How to Use the finally Block in Java, The finally block is coded after a try catch block. The statements in the finally block are executed unconditionally, i.e., regardless of whether an exception was​  Some resource cleanup, such as closing a file, needs to be done even if an exception is thrown. To do this, you can use a finally block. A finally block always executes, regardless of whether an exception is thrown. The following code example uses a try/catch block to catch an ArgumentOutOfRangeException.

Comments
  • I don't believe this is a duplicate. The linked question is tagged as Java and this one is about JavaScript. The answers happen to be the same but marking it as a duplicate suggests that Java and JavaScript is the same, which they quite clearly aren't.
  • "The clean up code can be put inside the catch." - No. The cleanup code must run both when the code in the try block completes successfully and when it throws.
  • Can you do that in javascript?
  • In your example why not just call hide(d) after the catch block, instead of inside a finally. Either way the code will run through the try/catch and then run hide(d), so there doesn't seem to be any point to using finally?
  • almost, it will also execute if you return something in the catch block
  • This does not answer the question and is not even Javascript-related at all
  • This question is about JavaScript