Try-with NPM | npm.io

try-with

A utility for safe and convenient handling of managed resources in JavasScript.

The purpose of this utility is to provide a convenient and safe way of using resources that must be manually released, such as remote connections and file handlers.

Similar concepts:

try-with-resource in Java
using statement in C#.

Installing

npm: npm i try-with
yarn: yarn add try-with

Example

A potential resource leak due to stream not being closed:

const stream = fs.createWriteStream(filePath);
// Next line will throw if `data` is not one of the allowed types.
stream.write(data);
// Will never be called if previous line threw and someone caught the error.
stream.close();

A safe variant of the above code:

const stream = fs.createWriteStream(filePath);
try {
  stream.write(data);
} finally {
  stream.close();
}

Functionally equivalent to the code above but using try-with:

const tryWith = require('try-with');

tryWith(fs.createWriteStream(filePath), stream => {
  stream.write(data);
});

API

tryWith(object, action, [cleanupMethodOrName])

Invokes action, passing object to it as a parameter.
After action is finished try to perform cleanup:
1. If third argument was omitted:
  1. If dispose property exists on object, try to invoke it.
  2. Else if close property exists on object, try to invoke it.
2. Else If third argument was provided and is a function, invoke it and pass object to it as a paramter.
3. Else (third argument was provided but is not a function):
  1. If it is a string or a symbol, try to invoke a property with that key on object.
  2. Else convert third argument to string and try to invoke a property with that key on object.
If an error was thrown when action was invoked, rethrow it.