A pretty printer for Javascript objects that looks like Ruby's pp formatter. In use on Rhino, untested elsewhere.

prettyprint.js

function pp(object, depth, embedded) { 
  typeof(depth) == "number" || (depth = 0)
  typeof(embedded) == "boolean" || (embedded = false)
  var newline = false
  var spacer = function(depth) { var spaces = ""; for (var i=0;i<depth;i++) { spaces += "  "}; return spaces }
  var pretty = ""
  if (      typeof(object) == "undefined" ) { pretty += "undefined" }
  else if ( typeof(object) == "boolean" || 
            typeof(object) == "number" ) {    pretty += object.toString() } 
  else if ( typeof(object) == "string" ) {    pretty += "\"" + object + "\"" } 
  else if (        object  == null) {         pretty += "null" } 
  else if ( object instanceof(Array) ) {
    if ( object.length > 0 ) {
      if (embedded) { newline = true }
      var content = ""
      for (var item in object) { content += pp(item, depth+1) + ",\n" + spacer(depth+1) }
      content = content.replace(/,\n\s*$/, "").replace(/^\s*/,"")
      pretty += "[ " + content + "\n" + spacer(depth) + "]"
    } else { pretty += "[]" }
  } 
  else if (typeof(object) == "object") {
    if ( Object.keys(object).length > 0 ){
      if (embedded) { newline = true }
      var content = ""
      for (var key in object) { 
        content += spacer(depth + 1) + key.toString() + ": " + pp(object[key], depth+2, true) + ",\n" 
      }
      content = content.replace(/,\n\s*$/, "").replace(/^\s*/,"")
      pretty += "{ " + content + "\n" + spacer(depth) + "}"
    } else { pretty += "{}"}
  }
  else { pretty += object.toString() }
  return ((newline ? "\n" + spacer(depth) : "") + pretty)
}

prettyprint_output.js

js> pp({foo:"bar", baz: 1})
{ foo: "bar",
  baz: 1
}
js> var taco
js> pp({foo:"bar", baz: [1,"taco",{"blarg": "moo", "mine": "craft"}, null, taco, {}], bleep: {a:null, b:taco, c: []}})
{ foo: "bar",
  baz: 
    [ 1,
      "taco",
      { blarg: "moo",
        mine: "craft"
      },
      null,
      undefined,
      {}
    ],
  bleep: 
    { a: null,
      b: undefined,
      c: []
    }
}

edited line 16: from 'for each' to 'for' since it was causing syntax errors in chrome...