Object.entries()

Why Object.entries?

The Object.entries () method is used to rotate the array of [key,values] ​​entered as parameters. The ordering of the properties is the same as that given by looping over the property values of the object manually.

Syntax:

Object.entries(obj)

• obj: Returns the [key, value] pairs with enumerable property.
• return: Object.assign () returns an array of [key, value] pairs of the enumerable property of the transmitted object.

Exceptions :

• It causes a TypeError if the argument passed is not an object .
• It causes a RangeError if the key passed in the argument is not in the range of the property[key, value] pair .

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JavaScript Object.entries Examples

Example 1

In the code example below, we did the following:

• First, we created an object called “animals.”
• We entered certain values ​​in the Animals object. (bear, cat, dog, rabbit)
• Then we created a variable called “animalsInfo”.
• We applied this variable “new Map”. And we applied the Object.entries method into it. In this way, we have reached the object of animals.

        let animals = {
            bear: "bear",
            cat: "cat",
            dog: "dog",
            rabbit: "rabbit"
        };

        let animalsInfo = new Map(Object.entries(animals));

        console.log(animalsInfo.has("cat"));
        console.log(animalsInfo.size);
        console.log(animalsInfo.get("dog"));

output:

true
4
dog

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Example 2

We have created an object named myNumbers. We entered certain values ​​into this object. And we called these values ​​with Object.entries ().

        let myNumbers = {
            first: 1,
            second: 2,
            third: 3
        }

        console.log(Object.entries(myNumbers)[0]);
        console.log(Object.entries(myNumbers)[1]);
        console.log(Object.entries(myNumbers)[2]);

output:

[“first”, 1]
[“second”, 2]
[“third”, 3]

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Example 3

        let myObject = {
            name: "rick",
            surname: "quenn"
        }

        console.log(Object.entries(myObject));
        console.log(Object.entries(myObject)[0]);
        console.log(Object.entries(myObject)[1]);

output:

0: (2) [“name”, “rick”]
1: (2) [“surname”, “quenn”]
length: 2  

[“name”, “rick”]
[“surname”, “quenn”]

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Example 4

        let myObject = Object.create({}, {
            getname: {
                value() {
                    return this.name;
                }
            }
        });

        myObject.name = "alex";
        console.log(Object.entries(myObject))

output:

[Array(2)]
> 0: (2) [“name”, “alex”]
> length: 1

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Polyfill

if (!Object.entries) {
  Object.entries = function( obj ){
    var ownProps = Object.keys( obj ),
        i = ownProps.length,
        resArray = new Array(i); // preallocate the Array
    while (i--)
      resArray[i] = [ownProps[i], obj[ownProps[i]]];
    
    return resArray;
  };
}

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Resources:

• https://developer.mozilla.org
• https://www.geeksforgeeks.org
• https://alligator.io
• https://stackoverflow.com

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Browser Support

Chrome	5
Edge	yes
Firefox	4
Internet Explorer	9
Opera	11.6
Safari	5
Android webview	yes
Chrome for Android	yes
Edge mobile	yes
Firefox for Android	4
Opera Android	11.5