# ti-longjohn

> Longjohn rewrite for Titanium

Latest version **0.0.5** (published 2015-04-06) · MIT license · 0 weekly downloads

## Install

```sh
npm install ti-longjohn
pnpm add ti-longjohn
yarn add ti-longjohn
bun add ti-longjohn
```

## Health

**Score 15/100 (F)** — status: abandoned.

Positive: no vulnerabilities.

Warnings: low downloads; no types; no esm support; pre 1.0.

Negative: abandoned; low maintenance score.

## Facts

| | |
|---|---|
| Version | 0.0.5 |
| Published | 2015-04-06 |
| First published | 2015-04-05 |
| Weekly downloads | 0 |
| License | MIT |
| TypeScript types | none |
| Module format | CommonJS |
| Dependencies | 0 |
| Known vulnerabilities | 0 |
| Install scripts | no |
| GitHub stars | 2 |
| Author | Dr. Stefan Schimanski |
| Maintainers | sttts |
| Keywords | titanium, appcelerator, longjohn, backtrace, async, stack, trace |

## Links

- npm: https://www.npmjs.com/package/ti-longjohn
- Repository: https://github.com/sttts/ti-longjohn
- Issues: https://github.com/sttts/ti-longjohn/issues
- npm.io page: https://npm.io/package/ti-longjohn

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## Recent versions

- 0.0.5 (latest) — 2015-04-06
- 0.0.4 — 2015-04-06
- 0.0.2 — 2015-04-06
- 0.0.1 — 2015-04-05

## README

# ti-longjohn ![Appcelerator Titanium](http://www-static.appcelerator.com/badges/titanium-git-badge-sq.png)

Long stack traces for Titanium with configurable call trace length.

This module is a port and partially rewrite of the Node.js [longjohn](https://github.com/mattinsler/longjohn) for the Titanium platform.

In addition it has special support to patch [async.js](https://github.com/caolan/async)'s `queue`.

## Requirements

* [Titanium SDK 3.4+](http://www.appcelerator.com/titanium/titanium-sdk/)

## Supports

* iOS simulator and device
* Android *is untested*, probably will not work because Titanium's Android support is based on V8, not JavaScriptCore.

## Installation

Download the latest release via git from github:

```bash
git clone https://github.com/sttts/ti-longjohn.git
```

or use [gittio](http://gitt.io):

```bash
gittio install ti-longjohn
```

or use [npm](https://www.npmjs.com):

```bash
npm install ti-longjohn
```

## Usage

To use ti-longjohn, require it in your code (probably in some initialization code). That's all!

```javascript
if (Ti.App.deployType !== 'production') {
  var longjohn = require('longjohn')(global);
}

// ... your code
```

where `global` is the global namespace. If you require `ti-longjohn` from the
`app.js` file, pass `this` as the global parameter.

### Output

When an exception is thrown, ti-longjohn will try to construct a long stack trace which can consist of multiple usual stack traces which are seperated by asyncronous callbacks, e.g. by `setTimeout`.

The output looks like this:

```
"TypeError at node_modules/nedb/lib/model.js:31",
"#0 () at node_modules/nedb/lib/datastore.js:296",
"#1 () at node_modules/nedb/lib/datastore.js:528",
"#2 () at node_modules/nedb/lib/cursor.js:174",
"#3 () at node_modules/nedb/lib/datastore.js:530",
"#4 () at node_modules/nedb/node_modules/async/lib/async.js:582",
"#5 () at node_modules/nedb/node_modules/async/lib/async.js:498",
"#8 () at node_modules/process/index.js:14",
"-------- process.nextTick ---------",
"#2 () at node_modules/nedb/node_modules/async/lib/async.js:499",
"#3 () at node_modules/nedb/node_modules/async/lib/async.js:503",
"#4 () at node_modules/nedb/lib/datastore.js:564",
"#5 () at node_modules/nedb/lib/executor.js:40",
"#8 () at node_modules/nedb/node_modules/async/lib/async.js:731",
"#9 () at node_modules/nedb/node_modules/async/lib/async.js:728",
"#10 () at node_modules/nedb/node_modules/async/lib/async.js:24",
"#13 () at node_modules/process/index.js:14",
"-------- async.queue.push ---------",
"#1 () at node_modules/nedb/lib/executor.js:56",
"#2 () at node_modules/nedb/lib/datastore.js:568",
"#3 () at models/thread.js:1687",
"#4 () at lib/async.js:122"
```

To get a stack trace, ti-longjohn uses the `err.backtrace` property of an
`Error` object thrown during an exception. It seems that JavaScriptCore in Titanium is not very verbose about function names (hence, the empty `()` in the stack traces).

Moreover, it cannot be guaranteed by `ti-longjohn` that the stack traces are always complete.

### Use in production

During execution of JavaScript code, ti-longjohn will keep a linked list of error objects in memory, each keeping a stack trace up to an async callback.

Moreover, in order to get a stack trace, a `try/catch` block is used which is known to be bad for performance.

For these reason it is not recommended to have ti-longjohn activated in production.

### Limit traced async calls

```javascript
longjohn.async_trace_limit = 5;   // defaults to 10
longjohn.async_trace_limit = -1;  // unlimited
```

### Patching async.js

The queue mechanism in async.js breaks the stack trace chain that ti-longjohn tries to build and which it prints on error.

There is special support to patch the async.js queue in such a way that proper long stack traces are created:

```javascript
var longjohn = require('ti-longjohn')(global);
longjohn.patch_async(require('async'));
```

Then the code

```javascript
var q = async.queue(function (x) {
    i.do.not.exist = x;
});
q.push(42, function done() {
    Ti.API.info('done');
});
```

will lead to a long stack trace:

```
"TypeError at app.js:19",
"#2 () at node_modules/async/lib/async.js:809",
"#5 () at node_modules/process/index.js:14",
"-------- async.queue.push ---------",
"#1 () at app.js:23"
```

---
_Source: https://npm.io/package/ti-longjohn · Machine-readable twin of the npm.io package page. Health data is recomputed on every publish._