Node.js - situation

Conveniently write status updates to a stream.

Why?

Constantly crafting status blocks in JavaScript intervals was a pain.

Installation

npm install --save situation

Example

Let's assume that you want to display the status of some variables every 2 seconds:

var situation = require('situation')

var obj = {cats: 1}
var dogs = 0

var s1 = situation()
  .watch('Cats', 'obj.cats')
  .watch('dogs')
  .watch('Animals', function(){ return obj.cats + dogs})
s1.eval = eval(s1.evalString)
s1.start('2 seconds')

//simulate change in variables
setInterval(function() {
  obj.cats += Math.floor((Math.random() * 5))
  connections += 1
},250)

the output is then displayed every on an interval:

*****************************************
*  Start Time: 2012-11-28T00:01:59.082Z *
*    Run Time: 0:0:15                   *
*        Cats: 125                      *
*        dogs: 63                       *
*     Animals: 188                      *
*****************************************

Members

situation(stream)

Creates a situation object. If no parameter is passed, process.stdout is the default stream.

Example:

var situation = require('situation')

var s1 = situation()
assert(s1.outStream, process.stdout) //true

watch([display], variableOrFunc)

Adds a variable to report the situation on. Must pass in as a string or a function. See the example.

Returns the situation object so that they can be chained.

eval

Object that contains the variable functions. Must be used in conjunction with evalString.

Note: Any variables used, must be available in the context of the eval method called. That is, where ever you call eval(situationObj.evalString) must have the variables in scope.

Example:

var situation = require('situation')

var s1 = situation().watch('counter')
s1.eval = eval(s1.evalString) //this must be called!!

evalString

See eval.

shouldOutputJSON

Instead of writing the text status block to the stream, a JSON object is written to the stream. This may be useful if writing to a TCP stream.

Example:

var situation = require('situation')

var processing = 55

var s1 = situation(myServer)
s1.shouldOutputJSON = true

/*  
    write to myServer TCP every 5 seconds
    date:
    {
      "startTime": "2012-11-28T00:01:59.082Z",
      "runTime": "0:0:15",
      "processing": 55
    }
*/
s1.start(5000)

start([updateInterval])

Sets an internal interval so that the stream can be written to at a repeated rate. Can either be a number or a string. If it's a number, it's assumed to be in milliseconds. If it's a string, it must be compatible with ms. If no parameter is passed the internal startTime will just be set, but no interval will run. You can then call update() manually.

stop()

If the internal update interval is running, this will stop it. This is equivalent to calling clearInterval, i.e. it'll remove it from the Node.js event run loop.

update()

Force a manual write to the stream of the current variable situation.

Example:

var situation = require('situation')

var processing = 55

var s1 = situation()
s1.start()

setInterval(function() {
  s1.update()
}, Math.floor(Math.random()*10000))

License

(MIT License)

Copyright 2012, JP Richardson [email protected]