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Created December 23, 2010 06:51
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a custom object inspector to help me understand JavaScript
function escapeString(string) {
string = string.replace(/\\/g, "\\\\").
replace(/\n/g, "\\n").
replace(/\r/g, "\\r").
replace(/\t/g, "\\t");
if (string.indexOf("'") < 0) {
return "'" + string + "'";
string = string.replace(/"/g, "\\\"");
return '"' + string + '"';
function escapeKey(string, enumerable) {
if (!enumerable) { return "[" + string + "]"; }
if ((/[a-z_$][a-z0-9_$]*/i).test(string)) {
return string;
return escapeString(string);
function getType(object) {
var proto = object.__proto__;
if (!(proto && proto.constructor)) { return ""; }
function inspect(value, keyer, short) {
if (value === undefined) { return "undefined"; }
if (value === null) { return "null"; }
if (value === true) { return "true"; }
if (value === false) { return "false"; }
switch (typeof value) {
case 'object':
case 'function':
if (short) {
return "(" + getType(value) + (Object.keys(value).length ? "..." : "") + ")";
var type = getType(value);
var parts = keyer(value).map(function (key, i) {
var prop = Object.getOwnPropertyDescriptor(value, key);
if (prop.hasOwnProperty("value")) {
return (i.toString() !== key ? escapeKey(key, prop.enumerable) + ": " : "") +
inspect(prop.value, keyer, true);
if (prop.get) {
if (prop.set) {
return escapeKey(key, prop.enumerable) + ": [Getter/Setter]";
return escapeKey(key, prop.enumerable) + ": [Getter]";
} else if (prop.set) {
return escapeKey(key, prop.enumerable) + ": [Setter]";
var body;
if (parts.length) {
body = " " + parts.join(", ") + " ";
if (body.length > 77 - type.length) {
body = "\n " + parts.join(",\n ") + "\n";
} else {
body = "";
return "(" + type + body + ")";
case 'number': return value.toString();
case 'string': return escapeString(value);
throw new Error("Not Implemented");
var types = {
Number: [Number, 42],
String: [String, "Hello"],
Date: [Date, new Date(],
RegExp: [RegExp, new RegExp("Find Me", "gi")],
Object: [Object, {name: "Tim", age: 28}],
Array: [Array, [1,2,3,4]],
Buffer: [Buffer, new Buffer(4)],
EventEmitter: [process.EventEmitter, process]
Object.keys(types).map(function (name) {
var type = types[name][0],
prototype = type.prototype,
example = types[name][1];
console.log("%s -> %s", name, inspect(type, Object.getOwnPropertyNames));
console.log("%s.prototype -> %s", name, inspect(prototype, Object.getOwnPropertyNames));
console.log("example %s -> %s\n", name, inspect(example, Object.getOwnPropertyNames));
var modules = ["http", "net", "url", "path", "querystring", "child_process", "step", "connect", "haml", "nstore"]; (name) {
console.log("%s -> %s", name, inspect(require(name), Object.getOwnPropertyNames));
Number -> (Function
[NaN]: NaN,
[arguments]: null,
[length]: 1,
[name]: 'Number',
[MAX_VALUE]: 1.7976931348623157e+308,
[prototype]: (Object),
[caller]: null,
[MIN_VALUE]: 5e-324
Number.prototype -> (Object
[toExponential]: (Function),
[toString]: (Function),
[toLocaleString]: (Function),
[toPrecision]: (Function),
[valueOf]: (Function),
[constructor]: (Function),
[toFixed]: (Function)
example Number -> 42
String -> (Function
[arguments]: null,
[length]: 1,
[name]: 'String',
[prototype]: (Object),
[fromCharCode]: (Function),
[caller]: null
String.prototype -> (Object
[length]: 0,
[constructor]: (Function),
[concat]: (Function),
[localeCompare]: (Function),
[substring]: (Function),
[italics]: (Function),
[charCodeAt]: (Function),
[strike]: (Function),
[indexOf]: (Function),
[toLowerCase]: (Function),
[trimRight]: (Function),
[toString]: (Function),
[toLocaleLowerCase]: (Function),
[replace]: (Function),
[toUpperCase]: (Function),
[fontsize]: (Function),
[trim]: (Function),
[split]: (Function),
[substr]: (Function),
[sub]: (Function),
[charAt]: (Function),
[blink]: (Function),
[lastIndexOf]: (Function),
[sup]: (Function),
[fontcolor]: (Function),
[valueOf]: (Function),
[link]: (Function),
[bold]: (Function),
[anchor]: (Function),
[trimLeft]: (Function),
[small]: (Function),
[search]: (Function),
[fixed]: (Function),
[big]: (Function),
[match]: (Function),
[toLocaleUpperCase]: (Function),
[slice]: (Function)
example String -> 'Hello'
Date -> (Function
[now]: (Function),
[arguments]: null,
[UTC]: (Function),
[length]: 7,
[name]: 'Date',
[prototype]: (Object),
[caller]: null,
[parse]: (Function)
Date.prototype -> (Object
[constructor]: (Function),
[toUTCString]: (Function),
[setMinutes]: (Function),
[setUTCMonth]: (Function),
[getMilliseconds]: (Function),
[getTime]: (Function),
[getMinutes]: (Function),
[getUTCHours]: (Function),
[toString]: (Function),
[setUTCFullYear]: (Function),
[setMonth]: (Function),
[getUTCMinutes]: (Function),
[getUTCDate]: (Function),
[setSeconds]: (Function),
[toLocaleDateString]: (Function),
[getMonth]: (Function),
[toTimeString]: (Function),
[toLocaleTimeString]: (Function),
[setUTCMilliseconds]: (Function),
[setYear]: (Function),
[getUTCFullYear]: (Function),
[getFullYear]: (Function),
[getTimezoneOffset]: (Function),
[setDate]: (Function),
[getUTCMonth]: (Function),
[getHours]: (Function),
[toLocaleString]: (Function),
[toISOString]: (Function),
[toDateString]: (Function),
[getUTCSeconds]: (Function),
[valueOf]: (Function),
[setUTCMinutes]: (Function),
[getUTCDay]: (Function),
[toJSON]: (Function),
[setUTCDate]: (Function),
[setUTCSeconds]: (Function),
[getYear]: (Function),
[getUTCMilliseconds]: (Function),
[getDay]: (Function),
[setFullYear]: (Function),
[setMilliseconds]: (Function),
[setTime]: (Function),
[setHours]: (Function),
[getSeconds]: (Function),
[toGMTString]: (Function),
[getDate]: (Function),
[setUTCHours]: (Function)
example Date -> (Date)
RegExp -> (Function
[$*]: [Getter/Setter],
$3: [Getter/Setter],
[$`]: [Getter/Setter],
[arguments]: null,
$9: [Getter/Setter],
rightContext: [Getter/Setter],
multiline: [Getter/Setter],
[length]: 2,
$7: [Getter/Setter],
lastParen: [Getter/Setter],
[$input]: [Getter/Setter],
[$+]: [Getter/Setter],
[$&]: [Getter/Setter],
[name]: 'RegExp',
leftContext: [Getter/Setter],
$8: [Getter/Setter],
$4: [Getter/Setter],
[prototype]: (Object),
$1: [Getter/Setter],
[$']: [Getter/Setter],
[$_]: [Getter/Setter],
input: [Getter/Setter],
[caller]: null,
lastMatch: [Getter/Setter],
$2: [Getter/Setter],
$5: [Getter/Setter],
$6: [Getter/Setter]
RegExp.prototype -> (Object
[toString]: (Function),
[constructor]: (Function...),
[exec]: (Function),
[compile]: (Function),
[test]: (Function)
example RegExp -> (RegExp
[lastIndex]: 0,
[multiline]: false,
[global]: true,
[source]: 'Find Me',
[ignoreCase]: true
Object -> (Function
[getOwnPropertyNames]: (Function),
[arguments]: null,
[seal]: (Function),
[length]: 1,
[create]: (Function),
[name]: 'Object',
[isFrozen]: (Function),
[keys]: (Function),
[prototype]: (),
[isExtensible]: (Function),
[getOwnPropertyDescriptor]: (Function),
[caller]: null,
[preventExtensions]: (Function),
[getPrototypeOf]: (Function),
[defineProperty]: (Function),
[isSealed]: (Function),
[defineProperties]: (Function),
[freeze]: (Function)
Object.prototype -> (
[toString]: (Function),
[__lookupGetter__]: (Function),
[__defineGetter__]: (Function),
[toLocaleString]: (Function),
[hasOwnProperty]: (Function),
[valueOf]: (Function),
[__defineSetter__]: (Function),
[constructor]: (Function),
[propertyIsEnumerable]: (Function),
[isPrototypeOf]: (Function),
[__lookupSetter__]: (Function)
example Object -> (Object age: 28, name: 'Tim' )
Array -> (Function
[arguments]: null,
[length]: 1,
[isArray]: (Function),
[name]: 'Array',
[prototype]: (Object),
[caller]: null
Array.prototype -> (Object
[length]: 0,
[constructor]: (Function),
[concat]: (Function),
[map]: (Function),
[sort]: (Function),
[join]: (Function),
[indexOf]: (Function),
[filter]: (Function),
[some]: (Function),
[toString]: (Function),
[reduceRight]: (Function),
[splice]: (Function),
[forEach]: (Function),
[shift]: (Function),
[unshift]: (Function),
[toLocaleString]: (Function),
[lastIndexOf]: (Function),
[reverse]: (Function),
[reduce]: (Function),
[pop]: (Function),
[push]: (Function),
[every]: (Function),
[slice]: (Function)
example Array -> (Array 1, 2, 3, 4, [length]: 4 )
Buffer -> (Function
byteLength: (Function),
[arguments]: null,
isBuffer: (Function),
[length]: 3,
[name]: 'Buffer',
poolSize: 8192,
[prototype]: (Object...),
[caller]: null,
_charsWritten: 264
Buffer.prototype -> (Object
binarySlice: (Function),
utf8Write: (Function),
utf8Slice: (Function),
toString: (Function),
inspect: (Function),
binaryWrite: (Function),
asciiSlice: (Function),
set: (Function),
copy: (Function),
write: (Function),
[constructor]: (Function...),
asciiWrite: (Function),
get: (Function),
slice: (Function)
example Buffer -> (Buffer 252, 131, 196, 4, length: 4, offset: 4048, parent: (SlowBuffer...) )
EventEmitter -> (Function
[arguments]: null,
[length]: 0,
[name]: 'EventEmitter',
[prototype]: (Object...),
[caller]: null
EventEmitter.prototype -> (Object
on: (Function),
removeListener: (Function),
addListener: (Function),
once: (Function),
removeAllListeners: (Function),
emit: (Function),
[constructor]: (Function),
listeners: (Function)
example EventEmitter -> (EventEmitter
mainModule: (Module...),
createChildProcess: (Function),
setuid: (Function),
binding: (Function),
on: (Function),
cwd: (Function),
mixin: (Function),
stdout: [Getter],
unwatchFile: (Function),
_tickCallback: (Function),
title: 'node',
compile: (Function),
error: (Function),
platform: 'PLATFORM',
env: (...),
version: 'v0.3.2',
getgid: (Function),
chdir: (Function),
reallyExit: (Function),
setgid: (Function),
assert: (Function),
execPath: '/home/tim/.nvm/v0.3.2/bin/node',
exit: (Function),
kill: (Function),
pid: 9310,
argv: (Array...),
getuid: (Function),
debug: (Function),
memoryUsage: (Function),
ARGV: (Array...),
ENV: (...),
removeListener: (Function),
openStdin: (Function),
_needTickCallback: (Function),
installPrefix: '/home/tim/.nvm/v0.3.2',
nextTick: (Function),
versions: (Object...),
watchFile: (Function),
_kill: (Function),
EventEmitter: (Function),
dlopen: (Function),
addListener: (Function),
inherits: (Function),
_byteLength: (Function),
umask: (Function)
http -> (Object
STATUS_CODES: (Object...),
cat: (Function),
parsers: (...),
Server: (Function...),
ClientRequest: (Function...),
ServerResponse: (Function...),
createServer: (Function),
IncomingMessage: (Function...),
OutgoingMessage: (Function...),
createClient: (Function),
Client: (Function...)
net -> (Object
isIPv6: (Function),
Server: (Function...),
Stream: (Function...),
createConnection: (Function),
createServer: (Function),
isIPv4: (Function),
isIP: (Function)
url -> (Object
resolveObject: (Function),
resolve: (Function),
format: (Function),
parse: (Function)
path -> (Object
extname: (Function),
join: (Function),
normalizeArray: (Function),
split: (Function),
normalize: (Function),
basename: (Function),
existsSync: (Function),
exists: (Function),
dirname: (Function)
querystring -> (Object
decode: (Function),
escape: (Function),
stringify: (Function),
unescapeBuffer: (Function),
unescape: (Function),
encode: (Function),
parse: (Function)
child_process -> (Object spawn: (Function), execFile: (Function), exec: (Function) )
step -> (Function
[arguments]: null,
fn: (Function),
[length]: 0,
[name]: 'Step',
[prototype]: (Object),
[caller]: null
connect -> (Object
middleware: (Object),
Server: (Function...),
createServer: (Function),
version: '0.5.0',
utils: (Object...)
haml -> (Function
render: (Function),
[arguments]: null,
[length]: 2,
[name]: 'Haml',
[prototype]: (Object),
execute: (Function),
[caller]: null,
optimize: (Function),
compile: (Function)
nstore -> (Object
remove: (Function),
genKey: (Function),
initialize: (Function),
save: (Function),
get: (Function),
[new]: (Function),
loadDatabase: (Function),
length: [Getter],
checkQueue: (Function)
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