How to get object properties using Object.keys method in JavaScript

Object.keys can be used to obtain the properties of an object. Object.keys returns an array whose elements are strings, whose elements come from the properties that can be directly enumerated from the given object. If used in an associative array, the key can be obtained. In this article, we will take a look at the specific use of Object.keys.

How to use Object.keys

First, let’s take a look at how to get the properties after creating an object.

How to create an object

First, let’s look at the most basic object creation method.

In short, the structure of an object is divided into "properties" and "methods".

Attributes can save various information in "keyword" and "value" pairs, similar to functions.

You can create an empty object as follows.

var obj1 = { } 
var obj2 = new Object()

The above two methods are the same. It is simpler to describe it like "obj1", so it is often used.

For example, you can write an object that contains properties with the person's "name" and "age" information, as shown below.

var obj = {
 
    name : '张 三',
    age : 30
 
}

Methods to get object properties

Now that we know how to create an object, let us use Object.keys to get the properties.

To use it, just specify the object as a parameter, such as [Object.keys(Object)].

Its characteristic is that it can obtain the array data of the enumeration property name as the return value.

Therefore, first prepare the following object data.

var obj = {
  name: '张 三',  
  age: 30,  
  area: '北京'
}

Please confirm the name/age/area 3 attributes here.

Next, use Object.keys() and write like this

var result = Object.keys(obj); 
console.log(result);

Execution result:

["name", "age", "area"]

You can retrieve all properties by specifying the object of the keys() parameter .

It can be seen from the execution results that the attribute name has been obtained as array data.

It is convenient to convert to such array data, because this can use various array methods provided in the JavaScript standard.

How to use Object.keys with arrays

To use Object.keys to get properties, specify the object to get in the parameter.

Let’s take a look at the following program.

var obj = ["sa", "mu", "ra", "i"];
console.log(Object.keys(obj));

Execution results: 0,1,2,3

In this way, we get the attributes.

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