Object
length number
name string
prototype object
create(proto, propertiesObject) function
Create a new object, using the specified prototype object and optional property descriptors.
proto: The object to be used as the prototype.
propertiesObject: Optional. An object specifying properties to be added.
Returns: A new object with the given prototype and properties.
getPrototypeOf(obj) function
Return the prototype of the specified object. If no prototype is found (e.g. the object has null as its prototype), return null.
obj: The object whose prototype is to be returned.
Returns: The prototype of 'obj', or null.
setPrototypeOf(obj, proto) function
Set the prototype of the specified object to the provided value. Throws a TypeError if the object is non-extensible and the prototype is changed.
obj: The object whose prototype is set.
proto: The new prototype or null.
Returns: The object 'obj' after setting its prototype.
defineProperty(obj, prop, descriptor) function
Define or modify a property on an object using a property descriptor, returning the object. Throws a TypeError if the descriptor is invalid.
obj: The object on which to define or modify a property.
prop: The name or Symbol of the property.
descriptor: A property descriptor object (e.g., {value, writable, get, set, ...}).
Returns: The object with the newly defined or updated property.
defineProperties(obj, props) function
Define new or modify existing properties on an object, given an object of property descriptors. Returns the modified object.
obj: The object on which to define or modify properties.
props: An object mapping property names to property descriptors.
Returns: The modified object.
getOwnPropertyNames(obj) function
Return an array of all own (non-Symbol) property names found directly on the given object, in the same order as a for...in loop would return.
obj: The object whose own property names are returned.
Returns: An array of strings that correspond to the properties.
getOwnPropertySymbols(obj) function
Return an array of all own Symbol properties found directly on the given object.
obj: The object to retrieve Symbol keys from.
Returns: An array of Symbol keys.
groupBy(obj, fn) function
Non-standard / Proposed. Group the own properties of an object according to the return value of a grouping function. Typically returns a new object whose keys are the group identifiers.
obj: The object to group.
fn: A function(key, value) => groupingKey, applied to each property.
Returns: An object where properties are grouped by the returned keys.
keys(obj) function
Return an array of the object's own enumerable (non-Symbol) property names, in the same order that a normal loop would.
obj: The object whose property names are to be returned.
Returns: An array of property names.
values(obj) function
Return an array of the object's own enumerable (non-Symbol) property values, in the same order as Object.keys().
obj: The object whose property values are to be returned.
Returns: An array of property values.
entries(obj) function
Return an array of [key, value] pairs for the object's own enumerable (non-Symbol) properties, in the same order as Object.keys().
obj: The object whose [key, value] pairs are to be returned.
Returns: An array of [key, value] pairs.
isExtensible(obj) function
Return a boolean indicating whether new properties can be added to the specified object.
obj: The object to test.
Returns: True if the object is extensible, otherwise false.
preventExtensions(obj) function
Prevent new properties from ever being added to an object. Existing properties are not affected.
obj: The object to mark as non-extensible.
Returns: The non-extensible object.
getOwnPropertyDescriptor(obj, prop) function
Return the property descriptor for a named property on the specified object, if it exists, otherwise undefined.
obj: The object in which to look for the property.
prop: The name or Symbol of the property.
Returns: The property descriptor, or undefined if not found.
getOwnPropertyDescriptors(obj) function
Return an object containing all own property descriptors for the given object, keyed by property names (and Symbols).
obj: The object to retrieve property descriptors from.
Returns: An object mapping property keys to property descriptors.
is(value1, value2) function
Compare two values for strict equality, like '===' but without special treatment for +0 and -0, and treating NaN as equal to NaN.
value1: A value to compare.
value2: Another value to compare.
Returns: True if both values are the same, otherwise false.
assign(target, sources) function
Copy all enumerable own properties from one or more source objects to a target object, returning the modified target.
target: The object to receive properties.
sources: One or more objects containing properties to copy.
Returns: The updated target object.
seal(obj) function
Seal an object, preventing new properties from being added and marking all existing properties as non-configurable. Values of present properties can still be changed if they are writable.
obj: The object to seal.
Returns: The sealed object.
freeze(obj) function
Freeze an object, preventing new properties from being added, existing properties from being removed, or current properties from being changed (to the extent permitted by property descriptors).
obj: The object to freeze.
Returns: The frozen object.
isSealed(obj) function
Check if an object is sealed. A sealed object has no configurable properties and is non-extensible.
obj: The object to test.
Returns: True if the object is sealed, otherwise false.
isFrozen(obj) function
Check if an object is frozen. A frozen object is sealed and all data properties are non-writable.
obj: The object to test.
Returns: True if the object is frozen, otherwise false.
__getClass() function
fromEntries(entries) function
Transform a list of key-value pairs into an object. The iterable argument should yield pairs [key, value], which become properties on the resulting object.
entries: An iterable of [key, value] pairs.
Returns: A new object formed from the given entries.
hasOwn(obj, prop) function
Return a boolean indicating whether the specified property exists on the object as a direct own property (similar to hasOwnProperty, but directly on Object).
obj: The object on which to check the property.
prop: The name or Symbol of the property to check.
Returns: True if the property is found on 'obj', otherwise false.
id(obj) function
Non-standard. Return a unique identifier for the given object, assigning one if necessary. The same object will always yield the same ID.
obj: The object to retrieve or assign a unique ID.
Returns: A unique identifier (string or number) associated with the object.
mixin(target, source) function
Copy all property descriptors from 'source' into 'target'.
target: The object that will receive properties.
source: The object whose properties are to be copied.
Returns: The updated 'target' object.