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 each (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: []
    }
}

I find it quite useful. Stuck it inside my App.jsx (fixing the recursive calls of course) and passed it down the tree of components. Really useful for quick debugging in the golang style.