Object.entries()

The

Object.entries() method returns an array of key-value pairs for the given object's own enumerable properties.

The order is the same as that returned when looping over the object using for...in (the difference being that the for-in loop also enumerates properties in the prototype chain).

Syntax

Object.entries(obj)

Parameters

obj: An object that can return key-value pairs of its enumerable properties.

Return value

An array of key-value pairs for the given object's own enumerable properties.

Description

Object.entries() returns an array whose elements are the arrays corresponding to the key-value pairs of enumerable properties found directly on object.The properties are in the same order as given by manually looping through the object's property values.

The parameter is an object

const obj = { name: 'xiaoming', age: 'seven',sex: 'man', grade: 'four' };const res = Object.entries(obj)console.log(res);

Run result:

The parameter is an array

const obj = [1,2,3,4,5,6]const res = Object.entries(obj)console.log(res);

Run result:

The parameter is an array (the array contains objects)

const obj = [1,2,3,4,5,6,{a:'a'},{b:'b'},{c:'c'}]const res = Object.entries(obj)console.log(res);

Run result:

The parameter is an array (the elements in the array are objects)

const obj = [{a:'a'},{b:'b'},{c:'c'}]const res = Object.entries(obj)console.log(res);

Run result:

Objectconverted to Map

The

new Map() constructor accepts an iterable of entries.With the help of the Object.entries method you can easily convert Object to Map.

const obj = { name: 'xiaoming', age: 'seven',sex: 'man', grade: 'four' };console.log(Object.entries(obj));const map = new Map(Object.entries(obj));console.log(map);

Run result:

Summary

Object.entries() can traverse the key value of an object in the form of an array. The result is the same as the result returned when for...in loops through the object, but it will not traverseits prototype properties.

Let me introduce myself first. The editor graduated from Shanghai Jiaotong University in 2013. I worked in a small company and went to big factories such as Huawei and OPPO. I joined Alibaba in 2018, until now.I know that most junior and intermediate java engineers want to upgrade their skills, they often need to explore their own growth or sign up to study, but for training institutions, the tuition fee is nearly 10,000 yuan, which is really stressful.Self-learning that is not systematic is very inefficient and lengthy, and it is easy to hit the ceiling and the technology stops.Therefore, I collected a "full set of learning materials for java development" for everyone. The original intention is also very simple. I hope to help friends who want to learn by themselves but don't know where to start, and at the same time reduce everyone's burden.Add the business card below to get a full set of learning materials