JavaScript Error Handling Patterns for reliable Applications
Throwing and catching is the easy part. Designing errors that survive production debugging is the hard part. Error handling is where amateur and professional code diverge. Throwing an Error and catching it is trivial; designing an error strategy that lets you diagnose production failures at three in the morning is hard. Over years of maintaining production JavaScript, I have settled on patterns that make errors informative without overwhelming callers with failure modes they cannot act on. Throw Typed Errors Throwing strings or generic Error instances loses information. I create error subclasses for each failure category my application cares about: ValidationError, AuthError, NetworkError, NotFoundError. Each carries structured fields relevant to that category. This lets catch blocks discriminate with instanceof and handle specific failures appropriately while letting unexpected errors propagate to the global handler. class NotFoundError extends Error { constructor(resource, id) { super(resource + ' not found: ' + id); this.name = 'NotFoundError'; this.resource = resource; this.id = id; } } Catch Narrowly A try/catch that wraps a large block catches everything, including bugs in your own logic that should not be silenced. I keep catch blocks as small…