Shared utilities for browsers and Node.js
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isomorph build status

Utilities extracted from my dual-sided projects, which can be shared between browsers and Node.js/io.js. This project is really a grab-bag, so modules are intended to be required individually as needed, e.g. for type-checking functions you would require('isomorph/is').


npm install isomorph

Browser bundles export a global isomorph variable.

Module APIs


Type-checking and more - anything which is a generic, reusable test which would naturally have a function name starting with "is".

Type-checking functions

is.Array, is.Boolean, is.Date, is.Error, is.Function, is.Number, is.Object, is.RegExp, is.String

Determines if the given input is of the specified type.

Content-checking functions


Determines if the given Object has any enumerable properties.


Utilities for working with Arrays.


Flattens the given Array in place (and returns it, for chaining).


Utilities for working with Functions.

func.bind(fn, context[, arg1, ...])

Binds the given function to the given execution context (this when the function is called) and partially applies any additional arguments given.

The following properties are available on the binding function:

__func__ - the function which is bound.

__context__ - the context to which the function is bound.


Utilities for working with Objects.

object.hasOwn(obj, propertyName)

Wrapped version of 1Object.prototype.hasOwnProperty()` - use to avoid the "hasOwnProperty trap", as described in An Object is not a Hash.


Returns the type of an object as a lowercase string:

object.type({}) // "object"
object.type([]) // "array"

object.extend(dest[, src1, ...])

The classic extend method - copies own properties from src arguments to dest, returning dest.

Does nothing for any src arguments which are falsy, so it's safe to pass in an options argument which is potentially undefined, e.g.:

function quiz(kwargs) {
 kwargs = object.extend({answer: 42, question: 'Meaning?'}, kwargs)
 // ...

object.inherits(childConstructor, parentConstructor)

The classic inherits method - puts parentConstructor's prototype in childConstructor's prototype chain, returning childConstructor.


Creates an Array of [property, value] pairs from an Object.


Creates an Object from an Array of [property, value] pairs.

function sortedFieldObj(fieldObj) {
   var fields = object.items(fieldObj)
   fields.sort(function(a, b) {
     return a[1].creationCounter - b[1].creationCounter
   return object.fromItems(fields)


Creates a lookup Object from an Array, coercing each item in the Array to String and adding it to a lookup Object as a property whose value is true:

var ALLOWED_TAGS = ['div', 'span', 'h1']
  , TAG_LOOKUP = object.lookup(ALLOWED_TAGS)

function elementify(tagName) {
   if (TAG_LOOKUP[tagName]) {
      console.log(tagName + ' is valid')
   else {
      console.log(tagName + ' is not allowed')

object.get(obj, prop, default)

If the object has an own property with the given name, returns its value, otherwise returns the given default.

object.pop(obj, prop, default)

If the object has an own property with the given name, deletes the property from the object and returns its value, otherwise returns the given default.

object.setDefault(obj, prop, default)

If the object has an own property with the given name, returns its value, otherwise sets the given default as the property and returns it.


Formatting utilities.

format.format(str[, r1, ...])

Replaces "%s" placeholders in the given string with positional arguments.

format.formatArr(str, arr)

Replaces "%s" placeholders in the given string with arguments passed as an Array.

To output a literal '%', escape percentage signs by doubling them up:

format.format('%% Complete: %s%%', 95) // '% Complete: 95%'

format.formatObj(str, obj)

Replaces "{varName}" placeholders in the given string with same-named properties from a given object.

To output a literal '{varName}', double up the opening brace:

format.formatObj('{{foo}={foo}, {{bar}={bar}', {foo: 1, bar: 2}) // '{foo}=1, {bar}=2'

format.fileSize(bytes[, threshold])

Formats a number of bytes as a file size with an appropriately-scaled unit. The threshold argument determines the point at which the next unit up is used, defaulting to 768.

File sizes are rounded to the second decimal point, with any trailing zeros being stripped off and the decimal point also being omitted if all decimals are zero.

format.fileSize(768) // '768 bytes'
format.fileSize(769) // '0.75 kB
format.fileSize(123456789) // '117.74 MB'


Regular Expression utilities.

re.findAll(regex, str[, flags])

Uses a regular expression (given as a String or a RegExp object) to find and return matches in the given String, in the vein of Python's re.findall.

If a single group is present in the RegExp, a list of matches will be returned. If more than one group is present, a list of lists of matches will be returned.

If regex is specified as a String, the flags argument can be used to specify the flags to be used when compiling the RegExp.


Utilities for working with query strings.


Creates an Object from a query string, providing values for names which are present more than once as an Array.


Creates a query string from an Object, expecting names with multiple values to be specified as an Array.


Utilites for creating copies of objects. This implementation is from Oran Looney's Deep Copy in JavaScript and exposes the same interface.


Creates a shallow copy of an object.


Creates a deep copy of an object.


Utilities for formatting and parsing times and dates.

Formatting Directives

The following formatting directives are supported by time.strftime and time.strptime:

Directive Meaning
%b Locale's abbreviated month name
%B Locale's full month name
%d Day of the month as a decimal number [01,31]
%H Hour (24-hour clock) as a decimal number [00,23]
%I Hour (12-hour clock) as a decimal number [00,12]
%m Month as a decimal number [01,12]
%M Minute as a decimal number [00,59]
%p Locale's equivalent of either AM or PM (only with %I)
%S Second as a decimal number [00,59]
%y Year without century as a decimal number [00,99]
%Y Year with century as a decimal number
%% A literal % character

time.strftime(date, format[, locale])

A partial implementation of strftime, which formats a Date according to a format string. An Error will be thrown if an invalid format string is given.

time.strpdate(string, format[, locale])

Parses time details from a string, based on a format string, returning a Date.

This is a convenience wrapper around time.strptime:

time.strptime(string, format[, locale])

A partial implementation of strptime, which parses time details from a string, based on a format string.

Returns an Array of numbers, each corresponding to a datetime field:

Index Represents Values
0 Year (for example, 2003
1 Month range [1,12]
2 Day range [1,31]
3 Hour range [0,23]
4 Minute range [0,59]
5 Second range [0,59]

This implementation largely takes its cue from the documentation for Python's time module, as documented at with the exception of seconds formatting, which is restricted to the range [00,59] rather than [00,61].


The time module has basic support for using locales when parsing and formatting dates.

time.defaultLocale - the code for the default locale - defaults to 'en'.

time.locales - an object defining locale details, with locale codes as its properties. Only contains the locale definition for 'en' by default.

time.getLocale(code) - retrieves the locale with the given code, falling back to just the language code and finally to the default locale if a locale can't be found.

Locale codes can consist of a language code (e.g. 'en') or a language and region code (e.g. 'en-GB').


Utilities for working with URLs.


Splits any well-formed URI into its parts - from

parseUri 1.2.2
(c) Steven Levithan <>
MIT License


Creates a URI from an object specification - from

makeURI 1.2.2 - create a URI from an object specification
(c) Niall Smart <>

MIT Licensed