js.md

Global Objects > Object

MDN Documentation

Global Object: Properties

Property	Description
Object.length	Indicates how many arguments a function expects (excluding the rest parameter). Has a value of 1.
Object.prototype	Represents the Object prototype object and allows adding new properties and methods to all objects of type Object.

Methods of the Object Constructor

Method	Description
Object.assign(target, ...sources)	Copies values of all enumerable own properties from one or more source objects to a target object. Returns the target object.
Object.create(proto)	Creates a new object with the specified prototype object and properties.
Object.defineProperty(obj, prop, descriptor)	Adds a named property described by a descriptor to an object.
Object.defineProperties(obj, props)	Adds named properties described by descriptors to an object.
Object.entries(obj)	Returns an array of [key, value] pairs of a given object's own enumerable string properties.
Object.freeze(obj)	Freezes an object to prevent modification or deletion of its properties.
Object.getOwnPropertyDescriptor(obj, prop)	Returns a property descriptor for a named property on an object.
Object.getOwnPropertyDescriptors(obj)	Returns all property descriptors for an object.
Object.getOwnPropertyNames(obj)	Returns an array of all enumerable and non-enumerable property names.
Object.getOwnPropertySymbols(obj)	Returns an array of all symbol properties directly on an object.
Object.getPrototypeOf(obj)	Returns the prototype of a specified object.
Object.is(value1, value2)	Compares if two values are the same, equating all NaN values.
Object.isExtensible(obj)	Checks if an object can be extended.
Object.isFrozen(obj)	Checks if an object is frozen.
Object.isSealed(obj)	Checks if an object is sealed.
Object.keys(obj)	Returns an array of enumerable string property names.
Object.preventExtensions(obj)	Prevents any extensions to an object.
Object.seal(obj)	Prevents deletion of properties from an object.
Object.setPrototypeOf(obj, prototype)	Sets the prototype of an object.
Object.values(obj)	Returns an array of values of enumerable string properties.

Object Instances and Object Prototype Object

(Object.prototype.property or Object.prototype.method)

Properties

Name	Description
obj.constructor	Specifies the function that creates an object's prototype.
obj.__proto__	Points to the object which was used as a prototype when the object was instantiated.

Methods

Name	Description
obj.hasOwnProperty(prop)	Returns a boolean indicating whether an object contains the specified property as a direct property of that object (not inherited).
prototypeObj.isPrototypeOf(object)	Returns a boolean indicating whether the object this method is called upon is in the prototype chain of the specified object.
obj.propertyIsEnumerable(prop)	Returns a boolean indicating if the internal ECMAScript [[Enumerable]] attribute is set.
obj.toLocaleString()	Calls toString().
obj.toString()	Returns a string representation of the object.
object.valueOf()	Returns the primitive value of the specified object.

Global Objects > Array

MDN Documentation

Global Object: Properties

Property	Description
Array.length	Reflects the number of elements in an array.
Array.prototype	Represents the prototype of the Array constructor.

Global Object: Methods

Method	Description
Array.from(arrayLike[, mapFn[, thisArg]])	Creates a new array from an array-like or iterable object.
Array.isArray(obj)	Checks if a variable is an array.
Array.of(...elements)	Creates a new array instance with the specified elements.

Instance Properties

Property	Description
arr.length	Reflects the number of elements in an array.

Instance: Mutator Methods

Method	Description
arr.copyWithin(target, start, end)	Copies elements within the array.
arr.fill(value, start, end)	Fills elements with a static value.
arr.pop()	Removes and returns the last element.
arr.flat()	Flattens nested arrays into a single array.
arr.push(...elements)	Adds elements to the end of the array.
arr.reverse()	Reverses the array in place.
arr.shift()	Removes and returns the first element.
arr.sort()	Sorts the array in place.
arr.splice(start, deleteCount, ...items)	Adds or removes elements.
arr.unshift(...elements)	Adds elements to the beginning of the array.

Instance: Accessor Methods

Method	Description
arr.at(index)	Returns the element at the specified index.
arr.concat(...values)	Combines arrays and/or values.
arr.includes(searchElement, fromIndex)	Checks if the array contains a value.
arr.indexOf(searchElement[, fromIndex])	Finds the index of a value or returns -1.
arr.join(separator)	Joins array elements into a string.
arr.lastIndexOf(searchElement, fromIndex)	Finds the last index of a value or returns -1.
arr.slice(begin, end)	Extracts a section into a new array.
arr.toString()	Converts the array to a string.
arr.toLocaleString(locales, options)	Converts the array to a localized string.

Instance: Iteration Methods

Method	Description
arr.entries()	Returns an iterator with key/value pairs.
arr.every(callback[, thisArg])	Tests if all elements pass a test.
arr.filter(callback[, thisArg])	Creates a new array with elements that pass a test.
arr.find(callback[, thisArg])	Finds the first element that satisfies the test.
arr.findIndex(callback[, thisArg])	Finds the index of the first element that satisfies the test.
arr.forEach(callback[, thisArg])	Executes a callback for each element.
arr.keys()	Returns an iterator with array keys.
arr.map(callback[, thisArg])	Creates a new array with the results of a callback.
arr.reduce(callback[, initialValue])	Reduces array values to a single value.
arr.reduceRight(callback[, initialValue])	Reduces array values from right to left.
arr.some(callback[, thisArg])	Tests if at least one element passes a test.
arr.values()	Returns an iterator with array values.