Object.getOwnPropertyNames() vs Object.keys()
Written byPhuoc Nguyen
Created
10 Jun, 2020
Category
JavaScript
#Differences
-
`Object.getOwnPropertyNames(obj)`
returns all the properties of the object`obj`
.`Object.keys(obj)`
returns all enumerable properties.They provide the same result unless you set`enumerable: false`
to any property.In the following example, the`screen`
object has two properties,`branch`
and`size`
.jsconst screen = {branch: 'Dell',size: '27inch',};Object.getOwnPropertyNames(screen); // ['branch', 'size']Object.keys(screen); // ['branch', 'size']Let's define one more property named`resolution`
but it is set as`enumerable: false`
:jsObject.defineProperties(screen, {resolution: {enumerable: false,value: '2560 x 1440',},});The`resolution`
property then doesn't appear in the list of`Object.keys`
:jsObject.getOwnPropertyNames(screen); // ['branch', 'size', 'resolution']Object.keys(screen); // ['branch', 'size'] -
For arrays,
`Object.getOwnPropertyNames`
includes an extra property named`length`
which is the size of the array.jsconst animals = ['dog', 'cat', 'tiger'];Object.keys(animals); // ['0', '1', '2']Object.getOwnPropertyNames(animals); // ['0', '1', '2', 'length']
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Phước Nguyễn