console-log-wrapper.js

/**
 * @desc  An attempt at persistent browser console log history
 * @note  How To Use:
 *          1) Copy/paste all below JS into the browsers JS console
 *          2) Use any of the console.log/debug/warn/error functions
 *          3) Refresh the page
 *          4) Repeat steps #1 & #2 a few times
 *          5) Execute export_console_logs via the browser console (passing the log type as the only argument) to get the log history
 * @see https://developer.mozilla.org/en-US/docs/Web/API/Web_Storage_API
 */

var CONFIG = {
  enable: true,
  wrap_methods: [ 'log', 'debug', 'warn', 'error' ],
  log_limit: 10,
  oem_methods: {
    names: Object.keys( Object.getOwnPropertyDescriptors(console) ),
    orig: Object.assign({}, window.console )
  }
}

function console_log_wrapper( method ){ 
  if ( ! method || typeof method !== 'string' )
    throw new Error('No method type to wrap defined')
  
  if ( CONFIG.oem_methods.names.indexOf( method ) === -1 )
    throw new Error('No such console method: ' + method )
    
  // Set original value
  if ( ! localStorage.getItem( 'console.'+method ) ){
    localStorage.setItem( 'console.'+method, 'Wrapper Initiated' )
    localStorage.setItem( 'count-console.'+method, 0 )
  }
  
  return function(){
    var log_history = localStorage.getItem( 'console.'+method ).split('\n')
    var log_count = parseInt(localStorage.getItem( 'count-console.'+method ))
    var new_log_count = log_count+1
    
    CONFIG.oem_methods.orig.debug('Current log history:', log_history.join('\n'))
    var log_args = Array.from(arguments)
    var d = new Date()

    var logmsg = "["+ d.toLocaleTimeString() + "] console."+method+"('"+ log_args.join("', '") +"')')"

    log_history.unshift(logmsg)

    localStorage.setItem( 'console.'+method, '['+new_log_count+'] '+logmsg + "\n" + log_history.slice( 0, CONFIG.log_limit-1 ).join('\n') )

    localStorage.setItem( 'count-console.'+method, new_log_count)

    CONFIG.oem_methods.orig.debug('updated '+method+':' + localStorage.getItem( 'console.'+method ))
    
    CONFIG.oem_methods.orig[ method ].apply( this, log_args )
  }
}

function export_console_logs( method ){
  var log_data = localStorage.getItem( 'console.' + method )
  var log_count = parseInt(localStorage.getItem( 'count-console.'+method ))

  if ( ! log_data )
    alert('No log data')
  else 
    alert('Data for console.'+method+':\n' + log_data)
}

if ( CONFIG.enable ) {
  CONFIG.wrap_methods.forEach(function( method ){
    if ( CONFIG.oem_methods.names.indexOf( method ) === -1 ){
      alert('No original console method named ' + method)
      return
    }
    
    var wrapped_fn = console_log_wrapper( method )
    
    console[method] = wrapped_fn
    window.console[method] = wrapped_fn
    
    CONFIG.oem_methods.orig.debug('[FACTORY] Wrapped console method:', method)
  })
}