JSPM

Because Logging can be pretty and fun

Installation

$ npm install draftlog

What it does

It allows you to re-write a line of your log after being written. Just like post 'updating'.

It does that by keeping track of the current lines of code written thorugh the stream, and moving the cursor up to the line of the LogDraft you created previously, and updating it's content.

How the HECK is that even possible?

Usage

// Setup
const DraftLog = require('draftlog')
DraftLog(console)

To create a updatable log, use the draft method injected into the provided console:

// Create a Draft log
var update = console.draft('Hy, my name is')

// You can call logs after it
console.log('Something else')

// Use the received callback to update it as many times as you want
update('Hy, my name is Ivan!')

Here is some interesting exemples:

// Prints a clock incrementing one every second in the same line
var draft = console.draft()
var elapsed = 1
setInterval( () => {
  draft('Elapsed', elapsed++, 'seconds')
}, 1000)

console.log('It doesn't matter')
console.log('How \n many \n lines \n ituses')

Or maybe, to show an flow process?

function someAsyncFunction(){ 
  var TAG = '[someAsyncFunction]'
  var log = console.draft(TAG, 'init')

  function a() {
    setTimeout(() => {
      log(TAG, 'calling b')
      b()
    }, 500)
  }

  function b() {
    setTimeout(() => {
      log(TAG, 'finished')
    })
  }
}

You can create your own progress bar, just like "that":

// progess goes from 0 to 100
function ProgressBar(progress) {
  // Make it 50 characters length
  progress = Math.round(progress / 2)
  return '[' + '='.repeat(progess) + ' '.repeat(100 - progress) + '] ' + progress + '%'
}

var barLine = console.draft('Starting download...')
downloadFile(function (progress) {
  barLine(ProgressBar(progress))
})

// Will show something like: (being updated in realtime)
// [============================                      ] 56%

Important things to know

Because of the way Terminals are built, it is not possible to update a text outside the viewing area of the terminal.

That said, DraftLogs are setup to automagically be rewritten on a new line if they reach the end of the viewport. Note that, you can disable that behavior, by setting DraftLog.defaults.canReWrite = false

Also, if the NodeJS environment cannot detect the number of rows of your terminal automatically, it will use the default height on DraftLog.defaults.maximumLinesUp. Modify that if needed.

Discouragements

This library is awesome for development, cli tools and what ever you want to created, that is NOT an optmized "slave" server. Please, disable it passing true as a seccond parameter to the DraftLog initialization:

// Disable Initialization (true = production; false = development)
DraftLog(console, true)

Creator

Ivan Seidel