for-each-property

for-each-property

Executes a callback for each property found on a object, with options regarding enumerability (enumerable or non-enumerable) and ownership (inherited or only own properties). It excludes built-in properties from Object and Function prototypes by default, and this behaviour can also be configured via options.

Goal

The goal is to provide a way to iterate through object's properties with a clean interface regarding enumerability and ownership, e.g. { enumerability: 'enumerable', inherited: true }. Also, discarding (or not, is an option) the built-in properties that may be found when looking up on the prototype-chain.

Currently JavaScript has some native methods to handle some cases, but not for all, and not with easy guessing names. Under the hood, the native methods available for some of the cases are being used. For example: Object.keys to enumerable and not inherited, for..into enumerable and inherited, Object.getOwnPropertyNames for own properties, not inherited, enumerable and nonenumerable.

Usage

const forEachProperty = require('for-each-property');

const object = {prop: 1, prop2: '2'};
const callback = (value, key) => console.log(value, key);
const options = {enumerability: 'enumerable', inherited: false};

forEachProperty(object, callback, options);

object: The object whose properties must be iterated on

callback: Function that will receive (value, key)

options:

• enumerability: The options are: 'enumerable' (default), 'nonenumerable' or 'all'

• inherited: The options are: true (default) or false

• excludeBuiltInPropsOf: An array of objects whose prototype properties must be excluded. It defaults to [Function, Object]

• excludeProps: An array properties that must be excluded. The default is ['prototype']

Example

Example testing all available cases, using an object created from a "parent", with properties enumerables and non-enumerables, inherited and not inherited;

const forEachProperty = require('for-each-property');

/////////////////////////////////////////
// OBJECT.CREATE FROM PARENT PROTOTYPE //
/////////////////////////////////////////

const Parent = function() {};

Parent.ParentEnumerableProp = 'ParentEnumerablePropVALUE';

Object.defineProperty(Parent.prototype, 'ParentEnumerablePropt', {
	configurable: true,
	enumerable: true,
	writable: true,
	value: 'ParentEnumerableProptVALUE'
});

Object.defineProperty(Parent.prototype, 'ParentNonEnumerableProto', {
	configurable: false,
	enumerable: false,
	writable: false,
	value: 'ParentNonEnumerableProtoVALUE'
});


Object.defineProperty(Parent, 'parentNonEnumerableProp', {
	configurable: false,
	enumerable: false,
	writable: false,
	value: 'parentNonEnumerablePropVALUE'
});

const objectCreatedFromParentProto = Object.create(Parent, {
	ownNonEmurableProp: {
		value: 'ownNonEmurablePropVALUE'
	},
	ownEmurableProp: {
		value: 'ownEmurablePropVALUE',
		enumerable: true
	}
});
objectCreatedFromParentProto.enumerableProp = 'enumerablePropVALUE';

//////////
// MAIN //
//////////

console.log(`========= For each own enumerable property =======`);
forEachProperty(objectCreatedFromParentProto, value => console.log(value), {enumerability: 'enumerable', inherited: false});

console.log(`========= For each own non-enumerable property =======`);
forEachProperty(objectCreatedFromParentProto, value => console.log(value), {enumerability: 'nonenumerable', inherited: false});

console.log(`========= For each own enumerable and non-enumerable property =======`);
forEachProperty(objectCreatedFromParentProto, value => console.log(value), {enumerability: 'all', inherited: false});

console.log(`========= For each enumerable property, including inherited properties =======`);
forEachProperty(objectCreatedFromParentProto, key => console.log(key), {enumerability: 'enumerable', inherited: true});

console.log(`========= For each non-enumerable property, including inherited properties =======`);
forEachProperty(objectCreatedFromParentProto, key => console.log(key), {enumerability: 'nonenumerable', inherited: true});

console.log(`========= For each enumerable and non-enumerable property, including inherited properties =======`);
forEachProperty(objectCreatedFromParentProto, key => console.log(key), {enumerability: 'all', inherited: true});

/////////////////////////
// CONSOLE.LOG RESULTS //
/////////////////////////

// === For each own enumerable property ===
// ownEmurablePropVALUE
// enumerablePropVALUE

// === For each own non-enumerable property ===
// ownNonEmurablePropVALUE

// === For each own enumerable and non-enumerable property ===
// ownNonEmurablePropVALUE
// ownEmurablePropVALUE
// enumerablePropVALUE

// === For each enumerable property, including inherited properties ===
// ownEmurablePropVALUE
// enumerablePropVALUE
// ParentEnumerablePropVALUE

// === For each non-enumerable property, including inherited properties ===
// ownNonEmurablePropVALUE
// parentNonEnumerablePropVALUE

// === For each enumerable and non-enumerable property, including inherited properties ===
// ownNonEmurablePropVALUE
// ownEmurablePropVALUE
// enumerablePropVALUE
// ParentEnumerablePropVALUE
// parentNonEnumerablePropVALUE