Omicron

Omicron (“O”) is a small JavaScript library of core functions and tools that assist with:

• Object manipulation and differential operations
• Prototypal inheritance
• Selected general tasks: safe typing, functional iteration, etc.

Contents

• Installation
• Usage
• API
• About this project

Installation

O has no dependencies; it can be loaded straight from the source file omicron.js, or installed via npm:

$ npm install omicron

In node, O will be available in the usual fashion:

var O = require('omicron');

In the browser, O will add a single object O to the global window (which can subsequently be reclaimed using O.noConflict()).

<script src="omicron.js"></script>

Usage

Example: Differential history

Consider a timeline object that efficiently stores history information. The differential functions of O can be used to make this a fairly straightforward task — in the code below, look for applications of functions delta and diff in particular, as well as usage of the special NIL object within the history array:

var O = require('omicron');

function Timeline () {
    var NIL = O.NIL,
        history = [
            {},
            { a: 1, b: 2 },
            { b: NIL, d: 4 },
            { a: NIL, e: 5 },
            { e: 2.718, f: 6 }
        ],
        index = 0;

    O.assign( this, {
        history: function () {
            return O.clone( history );
        },
        data: function () {
            return O.clone( history[ index ] );
        },
        back: function () {
            if ( index === 0 ) return;
            var subject = history[ index ];
            history[ index ] = O.delta( subject, history[ --index ] );
            return O.clone( history[ index ] = subject );
        },
        forward: function () {
            if ( index === history.length - 1 ) return;
            var subject = history[ index ];
            history[ index ] = O.delta( subject, history[ ++index ] );
            return O.clone( history[ index ] = subject );
        },
        push: function ( object ) {
            var l, n, subject = history[ index ];
            history[ index ] = O.delta( subject, object );
            history[ ++index ] = subject;
            l = index + 1;
            ( n = history.length - l ) && history.splice( l, n );
            return l;
        },
        replace: function ( object ) {
            var subject = history[ index ],
                d = O.diff( subject, object ),
                i;
            history[ index ] = object;
            index > 0 &&
                ( history[ i = index - 1 ] = O.diff( O.clone( object, d, history[i] ), object ) );
            index < history.length - 1 &&
                ( history[ i = index + 1 ] = O.diff( O.clone( object, d, history[i] ), object ) );
            return d;
        }
    });
}

Given the information preloaded into history, we can freely traverse a Timeline, forward and backward, and manipulate its history along the way. First let’s step forward:

var t = new Timeline;
t.data();    // {}
t.forward(); // { a:1, b:2 }
t.forward(); // { a:1, d:4 }              // History records 'b: NIL', so key 'b' was deleted
t.forward(); // { d:4, e:5 }              // Likewise, 'a: NIL' caused key 'a' to be deleted
t.forward(); // { d:4, e:2.718, f:6 }
t.forward(); // undefined                 // End of the timeline
t.data();    // { d:4, e:2.718, f:6 }

Note how the elements of history are being used to edit the data at history[ index ]. Note also how the special value NIL is used to encode that the key to which it’s assigned on the source operand should be deleted as part of the edit to the subject operand.

Next we’ll head back to where we started — but first, let’s glance back into the timeline to see how its contents have changed now that we’re positioned at the front end:

t.history();
// [
//   { a:NIL, b:NIL },
//   { b:2, d:NIL },
//   { a:1, e:NIL },
//   { e:5, f:NIL },
//   { d:4, e:2.718, f:6 }
// ]

The data is different, but it still records the exact same information. This is because the history elements are relative, and our perspective has changed after having moved forward four times — whereas the object initially contained the information needed to step forward in the timeline, viewing the timeline now from index = 4, its elements instead contain the information needed to step back to the original empty object at index = 0.

Traversing backward now:

t.back();    // { d:4, e:5 }
t.back();    // { a:1, d:4 }
t.back();    // { a:1, b:2 }
t.back();    // {}
t.back();    // undefined                 // Beginning of the timeline

And since we’ve gone back to where we started, the timeline elements will have transformed themselves to look just like they originally did:

t.history();
// [
//   {},
//   { a:1, b:2 },
//   { b:NIL, d:4 },
//   { a:NIL, e:5 },
//   { e:2.718, f:6 }
// ]

Next, let’s try pushing a new element into the middle of the history:

t.forward(); // { a:1, b:2 }
t.forward(); // { a:1, d:4 }
t.push( { b:2, c:3 } ); // 4            // The new length; `push` drops any forward elements
t.data();    // { a:1, b:2, c:3, d:4 }

t.history();
// [
//   { a:NIL, b:NIL },
//   { b:2, d:NIL },
//   { b:NIL, c:NIL },
//   { a:1, b:2, c:3, d:4 }
// ]

And finally, let’s replace an element, and examine its result and effects on the timeline:

t.back();    // { a:1, d:4 }
t.history();
// [
//   { a:NIL, b:NIL },
//   { b:2, d:NIL },
//   { a:1, d:4 }, // <---------- index
//   { b:2, c:3 }
// ]

t.replace( { a:4, b:3, d:1 } );
// { a:1, b:NIL, d:4 }

t.history();
// [
//   { a:NIL, b:NIL },
//   { a:1, b:2, d:NIL },
//   { a:4, b:3, d:1 }, // <----- index
//   { a:1, b:2, c:3, d:4 }
// ]

Calling replace instates the new element at index, adjusts the elements ahead and behind of the current index to reflect the new differentials, and returns the delta of the new element applied against the old element.

API

• Meta / Cached entities
• Special-purpose functions and objects
• Typing and inspection
• Iteration
• Object manipulation and differentiation
• Inheritance facilitators
• Array/Object composition
• Miscellaneous

Meta / Cached entities

VERSION

0.1.6

env

Environment variables.

• server : true if the environment conforms to the CommonJS module system (e.g., node.js).
• client : true in the case of a windowed environment (e.g. browser).
• debug : false. Changing this has no built-in effect. May be coded against by dependent libraries for their own purposes.

noConflict

Returns control of the global O property to its original value.

regexp

Regular expression store.

hasOwn

Object.prototype.hasOwnProperty

toString

Object.prototype.toString

slice

Array.prototype.slice

trim

String.prototype.trim, or shim.

create

Object.create, or partial shim.

getPrototypeOf

Object.getPrototypeOf, or partial shim.

Return to: Meta / Cached entities  <  API  <  top

Special-purpose functions and objects

noop

A function that returns undefined.

getThis

A function that returns this.

thunk

O.thunk( object )

Returns a lazy evaluator function that closes over and returns the provided object argument.

NIL

O.NIL

NIL is a special object used only for its unique reference. Whereas the null reference connotes “no object”, and undefined connotes “no value”, NIL specifically implies “no existence” of a corresponding property on some other object. The prime example is its use within edit and the related differential operation functions, where, within a given operand, a property whose value is set to NIL indicates the absence or deletion of the corresponding property on an associated operand.

Return to: Special-purpose functions and objects  <  API  <  top

Typing and inspection

type

O.type( object )

Returns the lowercase type string as derived from toString.

isNumber

O.isNumber( number )

Returns true if number is a valid numeric value.

isArray

O.isArray( array )

Returns true if array is a proper Array.

isFunction

O.isFunction( fn )

Returns true if fn is a function.

isPlainObject

O.isPlainObject( object )

Near identical port from jQuery. Excludes null, arrays, constructed objects, the global object, and DOM nodes.

isEmpty

O.isEmpty( object, [ andPrototype ] )

Returns a boolean indicating whether the object or array at object contains any members. For an Object type, if andPrototype evaluates to true, then object must also be empty throughout its prototype chain.

isEqual

O.isEqual( subject, object )

Performs a deep equality test between two objects.

var subject = { a:1, b:[ 'alpha', 'beta' ], c:{ d:1 } };

O.isEqual( subject, { a:1, b:[ 'alpha', 'beta' ], c:{ d:1 } } );         // true
O.isEqual( subject, { a:1, b:{ '1':'beta', '0':'alpha' }, c:{ d:1 } } ); // true

O.isEqual( [1], { 0:1, 1:undefined } ); // true
O.isEqual( { 0:1, 1:undefined }, [1] ); // false

lookup

O.lookup( object, path, [ separator ] )

Retrieves the value at the location indicated by the provided path string inside a nested object object.

var object = { a: { b:42 } };
O.lookup( object, 'a' );     // { b:42 }
O.lookup( object, 'a.b' );   // 42
O.lookup( object, 'a.b.c' ); // undefined

Return to: Typing and inspection  <  API  <  top

Iteration

each

O.each( object, callback )

Functional iterator with jQuery-style callback signature of key, value, object.

O.each( [ 'a', 'b', 'c' ], function ( index, string, array ) {
    array[ index ] = string.toUpperCase();
});
O.each( { x:3, y:4, z:5 }, function ( axis, value, vector ) {
    vector[ axis ] = value * value;
});

forEach

O.forEach( object, fn, context )

Functional iterator with ES5-style callback signature of value, key, object. If available, delegates to the native Array.prototype.forEach when appropriate.

O.forEach( [ 'a', 'b', 'c' ], function ( string, index, array ) {
    array[ index ] = string.toUpperCase();
});
O.forEach( { x:3, y:4, z:5 }, function ( value, axis, vector ) {
    vector[ axis ] = value * value;
});

Return to: Iteration  <  API  <  top

Object manipulation and differentiation

edit

O.edit( [ flags ], subject, source, [ ...sourceN ] )

Performs a differential operation across multiple objects.

By default, edit returns the first object-typed argument as subject, to which the contents of each subsequent source operand are copied, in order. Optionally the first argument may be either a Boolean deep, or a whitespace-delimited flags String containing any of the following keywords:

• deep : If a source property is an object or array, a structured clone is created on subject.

• own : Excludes source properties filtered by Object.hasOwnProperty.

• all : Includes source properties with undefined values.

• delta : Returns the delta, a structured object that contains the changes made to subject. If multiple source operands are provided, an array of deltas is returned. The delta can be used to store history information; immediately applying a returned delta array in reverse order using edit('deep', subject, ...) reverts subject to its original state (see example below).

• immutable : Leaves subject unchanged. Useful in certain applications where idempotence is desirable, such as when accompanied by the delta and absolute flags to produce a “diff” object.

• absolute : Processes against all properties in subject for each source, including those not contained in source.

Contains techniques and influences from the deep-cloning procedure of jQuery.extend, with which edit also retains a compatible API.

Alias: extend

O.edit( { a:1 }, { b:[ 'alpha', 'beta' ] } );
// { a:1, b:[ 'alpha', 'beta' ] }

O.edit( true, { a:1, b:[ 'alpha', 'beta' ] }, { b:[ undefined, 'bravo', 'charlie' ] } );
// { a:1, b:[ 'alpha', 'beta', 'charlie' ] }

O.edit( 'deep all', { a:1, b:[ 'alpha', 'beta' ] }, { b:[ undefined, 'bravo', 'charlie' ] } );
// { a:1, b:[ undefined, 'bravo', 'charlie' ] }

var _ = undefined, NIL = O.NIL,
    original, edits, object, deltas, reversion;

original = {
    a: 1,
    b: '2',
    c: {
        d: 3,
        e: 4
    },
    g: [ 0, 1 ]
};
edits = [
    { a: "uno" },
    { a: "un", b: "deux" },
    { c: { d: "III", e: "IV" } },
    { a: NIL, f: "Foo" },
    { b: "dos", g: [ _, "une" ] }
];

object = O.edit( true, {}, original );
// { b: "dos",
//   c: {
//       d: "III",
//       e: "IV"
//   },
//   f: "Foo",
//   g: [ 0, "une" ] }

deltas = O.edit.apply( O, [ 'deep delta', object ].concat( edits ) );
// [ { a: 1 },
//   { a: "uno", b: "2" },
//   { c: { d: 3, e: 4 } },
//   { a: "un", f: NIL },
//   { b: "deux", g: [ _, 1 ] } ]

reversion = O.edit.apply( O, [ true, object ].concat( deltas.reverse() ) );
// { a: 1,
//   b: "2",
//   c: {
//       d: 3,
//       e: 4
//   },
//   g: [ 0, 1 ] }

O.isEqual( original, reversion ); // true

See also: clone, delta, diff, assign

clone

O.clone( source, [ ...sourceN ] )

Creates a new object or array and deeply copies properties from all source operands.

See also: edit

var subject = { a:1, b:[ 'alpha', 'beta' ], c:{ d:1 } },
    object = O.clone( subject );

subject !== object;           // true
subject.b !== object.b;       // true
subject.b[0] === object.b[0]; // true
subject.c !== object.c;       // true
subject.c.d === object.c.d;   // true

delta

O.delta( subject, source, [ ...sourceN ] )

Deeply copies each source operand into subject, and returns a delta object, or an array of deltas in the case of multiple sources.

See also: edit

var NIL    = O.NIL,
    object = { a:1, b:[ 'alpha',   'beta'             ], c:{ d:1            } },
    edit   = {      b:[ undefined, 'bravo', 'charlie' ], c:{ d:NIL, e:2.718 } },
    delta  = O.delta( object, edit );

object;   // { a:1, b:[ 'alpha',   'bravo', 'charlie' ], c:{      e:2.718   } }
delta;    // {      b:[ undefined, 'beta',  NIL       ], c:{ d:1, e:NIL     } }

O.edit( 'deep', object, delta );
          // { a:1, b:[ 'alpha',   'beta'             ], c:{ d:1 } }

diff

O.diff( subject, source, [ ...sourceN ] )

Deeply compares each source operand to subject, and returns an absolute delta, or in the case of multiple source operands, an array of absolute deltas. Unlike the delta function, diff leaves subject unaffected.

See also: edit

var subject = { a:1, b:[ 'alpha', 'beta'  ], c:{ d:1          } },
    object  = {      b:[ 'alpha', 'bravo' ], c:{      e:2.718 } };

O.diff( subject, object ); // { a:1, b:[ undefined, 'beta' ], c:{ d:1, e:NIL } }

For plain objects subject and object, diff asserts the invariant:

O.isEqual( subject, O.edit( object, O.diff( subject, object ) ) ) === true

assign

O.assign( [ target ], map, [ value ] )

Performs batch assignments of values to one or more keys of an object.

O.assign( { a:1 }, { b:1, 'c d e f':2, 'g h i':3 } );
// { a:1, b:1, c:2, d:2, e:2, f:2, g:3, h:3, i:3 }

O.assign( { 'a b':1, c:2 } );
// { a:1, b:1, c:2 }

O.assign( 'a b c', 42 );
// { a: 42, b: 42, c: 42 }

O.assign( 'a b c' );
// { a: 'a', b: 'b', c: 'c' }

alias

O.alias( object, map )

Within object, copies a value from one key to one or more other keys.

O.alias( { a:1, c:2, g:3 }, {
    a: 'b'     
    c: 'd e f' 
    g: 'h i'   
});
// { a:1, b:1, c:2, d:2, e:2, f:2, g:3, h:3, i:3 }

Return to: Object manipulation and differentiation  <  API  <  top

Inheritance facilitators

inherit

O.inherit( child, parent, [ properties ], [ statics ] )

Facilitates prototypal inheritance between a child constructor and a parent constructor. In addition, child also inherits static members that are direct properties of parent.

• child and parent are constructor functions.

• properties (optional) is an object containing properties to be added to the prototype of child.

• statics (optional) is an object containing properties to be added to child itself.

function Animal () {}
Animal.prototype.eat = function () {
    return 'om nom nom';
};

O.inherit( Bird, Animal );
function Bird () {}
Bird.oviparous = true;
Bird.prototype.sing = function () {
    return 'tweet';
};

O.inherit( Chicken, Bird );
function Chicken () {}
Chicken.prototype.sing = function () {
    return 'cluck';
};

Chicken.oviparous;   // true
var c = new Chicken;
c.eat();             // "om nom nom"
c.sing();            // "cluck"

privilege

O.privilege( object, methodStore, map )

Generates partially applied functions for use as methods on an object.

Functions sourced from methodStore accept as arguments the set of variables to be closed over, and return the enclosed function that will become the object’s method.

The map argument maps a space-delimited set of method names to an array of free variables. These variables are passed as arguments to each of the named methods as found within methodStore.

This approach promotes reuse of a method’s logic by decoupling the function from the native scope of its free variables. A subsequent call to privilege, then, can be used on behalf of a distinct (though likely related) object to generate methods that are identical but closed over a distinct set of variables.

A limitation of this technique is the fact that, since partially applied values are copied when passed as arguments, there is no direct way for the external privileged method to change a value held within the constructor. In this case, one workaround is to provide a setter function that is scoped within the constructor; another alternative is simply to contain any desired “privileged” values as properties of a private object.

function Class () {
    var aPrivateObject = { attachment: 0 },
        aPrivateArray = [],
        aPrivateFunction = function () {};

    O.privilege( this, Class.privileged, {
        'aPrivilegedMethod aSimilarMethod' : [ aPrivateObject, aPrivateArray ],
        'aDifferentMethod' : [ aPrivateFunction ]
    });
}
Class.privileged = {
    aPrivilegedMethod: function ( thePrivateObject, thePrivateArray ) {
        function theActualMethod ( arg1, arg2 ) {
            thePrivateObject.attachment = arg1;
            thePrivateArray.push( arg2 );
        }
        return theActualMethod;
    },
    aSimilarMethod: function ( thePrivateObject, thePrivateArray ) {
        return function () { /*...*/ };
    },
    aDifferentMethod: function ( thePrivateFunction ) {
        return function ( arg ) {
            return thePrivateFunction( arg );
        };
    }
}

O.inherit( Subclass, Class );
function Subclass () {
    var myPrivateObject = { attachment: 'zero' },
        myPrivateArray = [];

    O.privilege( this, Class.privileged, {
        'aPrivilegedMethod aSimilarMethod' : [ myPrivateObject, myPrivateArray ],
        'aDifferentMethod' : [ aPrivateFunction ]
    });
}

var c = new Class;
c.aPrivilegedMethod( 1, 2 );

var sc = new Subclass;
sc.aPrivilegedMethod( 'one', 'two' );

Return to: Inheritance facilitators  <  API  <  top

Array/Object composition

flatten

O.flatten( object )

Extracts elements of nested arrays.

keys

O.keys( object )

Returns an object’s keys in an ordered string array.

invert

O.invert( array )

For an array whose values are unique key strings, this returns an object that is a key-value inversion of array.

Return to: Array/Object composition  <  API  <  top

Miscellaneous

stringFunction

O.stringFunction( fn )

Cyclically references a function’s output as its own toString property.

valueFunction

O.valueFunction( fn )

Cyclically references a function’s output as its own valueOf property.

Return to: Miscellaneous  <  API  <  top

About this project

Return to: top

