JavaScript Object Reference
Object Methods and Properties
Revised February 2026
| Name | Description |
|---|---|
| assign() | Copies properties from a source object to a target object |
| constructor | Returns the function that created an object's prototype |
| create() | Returns an object created from an existing object |
| defineProperties() | Adds or changes properties |
| defineProperty() | Adds or changes a property |
| delete | Deletes a property from an object: |
| entries() | Returns an array of the key/value pairs of an object |
| freeze() | Prevents any changes to an object |
| fromEntries() | Returns an object created from an iterable list of key/value pairs |
| getOwnPropertyDescriptor() | Returns an array of the keys of an object |
| getOwnPropertyDescriptors() | Returns an array of the keys of an object |
| getOwnPropertyNames() | Returns an array of the keys of an object |
| groupBy() | Groups object elements according to returned callback values |
| isExtensible() | Returns true if an object is extensible |
| isFrozen() | Returns true if an object is frozen |
| isSealed() | Returns true if an object is sealed |
| keys() | Returns an array of the keys of an object |
| preventExtensions() | Prevents adding new properties to an object |
| prototype | Lets you to add properties and methods to JavaScript objects |
| seal() | Prevents adding new or deleting existing object properties |
| toString() | Converts an object to a string and returns the result |
| valueOf() | Returns the primitive value of an object |
| values() | Returns an array of the property values of an object |
