javascript - Uses of the finally statement

Question

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.

Answer 1

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();