Non-obvious behaviors in Javascript foreach() loop

Wed, 07 Feb 2024 00:00:00 +0000

I want to show two inconspicuous-looking behaviors in Javascript foreach() loop that could confuse you while using it.

How to stop foreach loop in Javascript?

At first look pretty simple, inconspicuous-looking question, isn’t it? But it is Javascript… so any question could be tricky 😏

Let’s look at the sample code below (you can edit and run it)

It prints every number from array but return keyword is ineffective here. As is turns out, this is correct behavior according to documentation:

There is no way to stop or break a forEach() loop other than by throwing an exception.

So, we have only one way to stop this loop:

Now the loop is successfully stopped but… isn’t it looks like using cannon to kill a fly? So if you have to break loop you should consider to use e.g for loop instead foreach

Async function in foreach loop - will it work?

The second thing in foreach loop that could be misleading is:

foreach() expects a synchronous function - it does not wait for promises

Check this code:

As you can see, async function is not awaited.

Maybe for someone this two topics are obvious, but for me both of presented behaviors were unexpected (until today 😉).

Few ways to get current directory in .NET

Sun, 05 Nov 2023 00:00:00 +0000

Sometimes in our application, we need to obtain the current directory path. The purposes for doing so can vary: we might want to find a specific file or even load an external assembly. To achieve this, we have to determine the current location of our running application. .NET provides us with a few ways to do this, but some of them can be tricky in specific cases.

Property AppContext.BaseDirectory

In .NET this property returns path to directory that contains the entry point assembly (directory of the host executable). You could consider it like replacement for AppDomain.CurrentDomain.BaseDirectory from .NET Framework.

Directory.GetCurrentDirectory()

Returns the path from where you start the application. It won’t always be the same path as AppContext.BaseDirectory. For example if you run your .NET console application from Powershell in the directory where .exe file exists it returns:

PS D:\Application\bin\Debug\net7.0> .\Application.exe
Directory.GetCurrentDirectory() returns: D:\Application\bin\Debug\net7.0

but if you run the same app from parent folder it will return:

PS D:\Application> .\bin\Debug\net7.0\Application.exe
Directory.GetCurrentDirectory() returns: D:\Application

In the same way it will be work if you run your application which is hosted as Windows Service - then GetCurrentDirectory() method will return path to services.exe file: Windows\system32. So you should be aware if you use this method 😉

Property Environment.CurrentDirectory works in exactly the same way as Directory.GetCurrentDirectory() method.

Get location by reflection

You can also get current directory using reflection.
.NET offers two similar method: Assembly.GetExecutingAssembly().Location and Assembly.GetEntryAssembly().Location.
The difference between them is that GetExecutingAssembly() returns assembly that contains the code that is currently executing, while GetEntryAssembly() returns assembly that is the process executable in the default application domain, or the first executable that was executed by ExecuteAssembly(String).
For example if you run above methods in test project GetExecutingAssembly() will naturally return the test project assembly, but GetEntryAssembly() will return assembly of test runner (e.g. testhost.dll or ReSharperTestRunner.dll).
The usage of Assembly.GetExecutingAssembly().Location could be tricky in some scenarios. Consider a situation where you have main application that, in some way, uses an external assembly (e.g. load some plugin) as follows:

Assembly assembly = Assembly.LoadFrom($"{AppContext.BaseDirectory}\\plugins\\OtherProject.dll")

Note that desired dll is located in application subdirectory ‘plugins’.

If you call method from this assembly that uses GetExecutingAssembly() it returns the path to ‘plugins’ folder, not to the application directory.

Summary

I presented you only few - in my opinion most popular - ways to obtain the current dictionary path. More importantly I would like to emphasize that seemingly simple code be confusing when debugging our running application. 😉

Code with examples is available on my Github

Code Crumbs

Non-obvious behaviors in Javascript foreach() loop

How to stop foreach loop in Javascript?

Async function in foreach loop - will it work?

Few ways to get current directory in .NET

Summary