XML beautifier with attribute alignment

gistfile1.js

/* global process */

// A simple xml beautifier, based on the xml2js parser
// - align attribute names (this is what xmlbuilder can't do)
// - indent by 2 spaces

// Don't expect too much: 
// xml2js can't handle mixed element content: 
// <a>b<c/>d</a> is equal to <a>bd<c/></a> in the eyes of xml2js

(function(){

var fs     = require('fs')
var xml2js = require('xml2js')

if (process.argv.length < 3) {
  process.stderr.write("Please specify source xml file name")
  process.exit(1)
  }

fs.readFile( process.argv[2], 'utf8', onSuccess( function(data) {
    var parser = new xml2js.Parser()
    parser.parseString(data, onSuccess( function(xjson) {
      var lines = beautify(xjson)
      process.stdout.write(lines.join('\n'))        
      }))      
  }))

function onSuccess(f) {
  return function(err,data) {
    if (err) console.dir(err)
    else f(data)
    }
}

function beautify(xjson) {

  var indent = ""  
  var lines = []
  traverse(xjson)
  return lines

  function traverse(node, name ) {
    
    if (name === undefined)   return handleRoot()       
    if (typeof node == "string") return handleTextContent()             
    if (node instanceof Array)   return handleArray()
            
    handleOpenElement() 
    handleElementContent()       
    handleCloseElement()
    
    function handleRoot() {
      console.assert(typeof node == "object", "Call beautify with a JSON object")
      var keys = Object.keys(node)
      console.assert(keys.length == 1, "An XML object must have exactly 1 root element")        
      traverse( node[keys[0]], keys[0] )
      }      
    
    function handleOpenElement() {
      var line = indent + "<" + name
      if (node.hasOwnProperty("$")) handleAttributes()
      line += ">"
      lines.push(line)
      indent += "  "      

      function handleAttributes() {
        line += " "
        var attindent = line.replace(/./g," ")
        var numatts = Object.keys(node.$).length
        Object.keys(node.$).forEach( function(attname,i) {
          var att = attname + '="' + node.$[attname].replace(/"/g,'&#34') + '"'
          line += att
          if (i==numatts-1) return
          lines.push(line)
          line = attindent
          })
        }
    }

    function handleElementContent() {
      Object.keys(node)
        .filter( function(key) { return key!='$' })
        .forEach( function(key) {
          var y = node[key]
          traverse(y,key)
          })              
      }    

    function handleTextContent() {
      if (node) lines.push( indent + node )
      }                  

    function handleCloseElement() {
      indent = indent.slice(0,-2)
      lines.push( indent + "</" + name + ">" )
      }

    function handleArray() {
      // empty element
      if ( (node.length == 1) && (node[0] === '')) {
        lines.push(indent+'<'+name+'/>')
        }
      // xml2js way of denoting successive elements of the same element name
      node.forEach( 
        function(item) { traverse(item,name) } 
        )        
      }
            
    }
    
  
  }

})()