better-stack-traces

Better Stack Traces

Ever find yourself digging line-by-line through a Javascript stack trace to find the "real" error?

Error: ENOENT, no such file or directory '/bad/file/path'
    at Object.openSync (fs.js:230:18)
    at Object.readFileSync (fs.js:120:15)
    at readMyFile (/path/to/some/code/example.js:10:6)
    at doStuff (/path/to/some/code/example.js:5:10)
    at Object.<anonymous> (/path/to/some/code/example.js:13:1)
    at Module._compile (module.js:441:26)
    at Object..js (module.js:459:10)
    at Module.load (module.js:348:31)

With better-stack-traces, you get inline code snippets instead:

Error: ENOENT, no such file or directory '/bad/file/path'
    at Object.openSync (fs.js:230:18)
    at Object.readFileSync (fs.js:120:15)
    at readMyFile (/path/to/some/code/example.js:10:6)
    ──────────────────────────────────────────────────
     8 » 
     9 » function readMyFile(filePath) {
    10 »   fs.readFileSync(filePath);
    •••••••••••
    11 » }
    12 » 
    13 » doStuff(readMyFile)
    
    at doStuff (/path/to/some/code/example.js:5:10)
    ───────────────────────────────────────────────
    3 » 
    4 » function doStuff(readCallback) {
    5 »   return readCallback("/bad/file/path");
    ••••••••••••••
    6 » }
    7 » 
    8 » 
    
    at Object.<anonymous> (/path/to/some/code/example.js:13:1)
    ──────────────────────────────────────────────────────────
    11 » }
    12 » 
    13 » doStuff(readMyFile)
    ••••••
    
    at Module._compile (module.js:441:26)
    at Object..js (module.js:459:10)
    at Module.load (module.js:348:31)

Usage

1. Install the module using npm install better-stack-traces
2. At the top of your code, require("better-stack-traces").register()

• Alternatively, require("better-stack-traces/register"). This is useful for tools that have commandline options like --require in mocha.

1. Enjoy easier-to-read stack traces

Using better-stack-traces with CoffeeScript

If you develop with CoffeeScript, better-stack-traces will automatically compile .coffee files when rendering the trace. Maybe someday we will have proper line number mapping, but until then better stack traces might help your sanity :)

Customizing the output

Stack traces not quite better enough? There are a few options to tweak the output:

require("better-stack-traces").register({
  before: 2, // number of lines to show above the error
  after: 3, // number of lines to show below the error
  maxColumns: 80, // maximum number of columns to output in code snippets
  collapseLibraries: /node_modules/ // omit code snippets from paths that match the given regexp (ignores node_modules by default)
})

If you want to get really fancy, take a look at the library itself. You can subclass BetterStackTrace and register your customized subclass instead.

Related resources

If you find better-stack-traces useful, you might be interested in these:

• V8 Stack Trace API
• Tips for V8 stack formatting
• Long stack traces (for event handlers)

Contributors

• Wilker Lúcio (wilkerlucio)
  • allow regex for collapseLibraries