Object

The Object() constructor turns the input into an object. Its behavior depends on the input's type.

The Object.assign() static method copies all Object/propertyIsEnumerable Object/hasOwn from one or more source objects to a target object. It returns the modified target object.

The constructor data property of an Object instance returns a reference to the constructor function that created the instance object. Note that the value of this property is a reference to the function itself, not a string containing the function's name.

The Object.create() static method creates a new object, using an existing object as the prototype of the newly created object.

The Object.defineProperties() static method defines new or modifies existing properties directly on an object, returning the object.

The Object.defineProperty() static method defines a new property directly on an object, or modifies an existing property on an object, and returns the object.

The Object.entries() static method returns an array of a given object's own enumerable string-keyed property key-value pairs.

The Object.freeze() static method freezes an object. Freezing an object prevents extensions and makes existing properties non-writable and non-configurable. A frozen object can no longer be changed: new properties cannot be added, existing properties cannot be removed, their enumerability, configurability, writability, or value cannot be changed, and the…

The Object.fromEntries() static method transforms a list of key-value pairs into an object.

The Object.getOwnPropertyDescriptor() static method returns an object describing the configuration of a specific property on a given object (that is, one directly present on an object and not in the object's prototype chain). The object returned is mutable but mutating it has no effect on the original property's configuration.

The Object.getOwnPropertyDescriptors() static method returns all own property descriptors of a given object.

The Object.getOwnPropertyNames() static method returns an array of all properties (including non-enumerable properties except for those which use Symbol) found directly in a given object.

The Object.getOwnPropertySymbols() static method returns an array of all symbol properties found directly upon a given object.

The Object.getPrototypeOf() static method returns the prototype (i.e., the value of the internal [[Prototype]] property) of the specified object.

The hasOwnProperty() method of Object instances returns a boolean indicating whether this object has the specified property as its own property (as opposed to inheriting it).

The Object.is() static method determines whether two values are the same value.

The Object.isExtensible() static method determines if an object is extensible (whether it can have new properties added to it).

The Object.isFrozen() static method determines if an object is Object/freeze.

The isPrototypeOf() method of Object instances checks if this object exists in another object's prototype chain.

The Object.isSealed() static method determines if an object is sealed.

The Object.keys() static method returns an array of a given object's own enumerable string-keyed property names.

The Object.preventExtensions() static method prevents new properties from ever being added to an object (i.e., prevents future extensions to the object). It also prevents the object's prototype from being re-assigned.

ES2015 behavior for non-object argument

The propertyIsEnumerable() method of Object instances returns a boolean indicating whether the specified property is this object's enumerable own property.

The Object.seal() static method seals an object. Sealing an object prevents extensions and makes existing properties non-configurable. A sealed object has a fixed set of properties: new properties cannot be added, existing properties cannot be removed, their enumerability and configurability cannot be changed, and its prototype cannot be re-assigned. Values…

The Object.setPrototypeOf() static method sets the prototype (i.e., the internal [[Prototype]] property) of a specified object to another object or null.

The toString() method of Object instances returns a string representing this object. This method is meant to be overridden by derived objects for custom type coercion logic.

The valueOf() method of Object instances converts the this value to an object. This method is meant to be overridden by derived objects for custom type conversion logic.

The Object.values() static method returns an array of a given object's own enumerable string-keyed property values.

Shorthand notation for object literals

An object initializer is a comma-delimited list of zero or more pairs of property names and associated values of an object, enclosed in curly braces ({}). Objects can also be initialized using Object.create() or by invoking a constructor function with the new operator.

Computed property names

Shorthand method names

Shorthand property names

Spread properties

The optional chaining (?.) operator accesses an object's property or calls a function. If the object accessed or function called using this operator is undefined or null, the expression short circuits and evaluates to undefined instead of throwing an error.