exceptions.md

Proper exception handling

With the movement away from passages as .tw files error handling is getting more important, especially proper cleanup.

Good example is this issue, the end week animation did not stop because App.EndWeek.slaveAssignmentReport() failed, which meant that the endweek animation stop call wasn't executed.

Finally

Example of the proper way to handle code that cleans up something and should therefore always be executed:

try {
    // setup code

    // other code, may fail
} finally {
    // cleanup code
}

Do note that this will still propagate the error up, it will just execute cleanup code first. If you want to handle the error use catch

Catch

If needed a catch clause can be used as well, but it is usually advisable to only catch specific errors and only if you know they can be thrown and there is no easy way to prevent them.

Example with catch:

try {
    // code that may throw a RangeError
}  catch (ex instanceof RangeError) {
    // error handling code
}

Reference

See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/try...catch