Javascript Object.keys() Method – Get Array of keys from Object and Array

Posted on November 24, 2020January 23, 2021 by Mr Writer

Javascript Object.keys() method returns array of keys on given object.It takes Object or array as argument.

Syntax

Object.keys(obj)

It will return the keys of only those properties/methods whose enumarable property is set to true.

Examples

Using simple Object

person = {
    "fname" : "John",
    "lname" : "snow",
};
Object.keys(person);

//Console Output
(3) ["fname", "lname"]

Retriving keys of Object using Javascript Object.keys()

Object with method get_full_name

person = {
    "fname" : "John",
    "lname" : "snow",
    "get_full_name" : function(){
        console.log(this.fname+" "+this.lname)
    }
};
Object.keys(person);

//Console Output
(3) ["fname", "lname", "get_full_name"]

Object.keys() will also displays function name in key array

Even function name will also be returned by .keys() method.

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Object get_full_name method enumarable property to false

person = {
    "fname" : "John",
    "lname" : "snow",
};
Object.defineProperty(person, "get_full_name", {
    get: function() {
        console.log(this.fname+" "+this.lname)
    },
    enumarable : false
});
Object.keys(person);

//Console Output
(3) ["fname", "lname"]

Object lname property enumarable property to false

person = {
    "fname" : "John",
};
Object.defineProperty(person,'lname', {
    value : "snow",
    enumarable : false
});
Object.keys(person);

//Console Output
(3) ["fname"]

Skipping a property from including into keys by setting enumerable property as false

Setting option enumarable of property `lname` will exclude it from array.

Using array on Object.keys()

arr = ["one", "two", "three"];
Object.keys(arr);

//Console Output
(3) ["0", "1", "2"]

Using string on `Object.keys()

str = "Javascript";
Object.keys(str);

//Console Output
(10) ["0", "1", "2", "3", "4", "5", "6", "7", "8", "9"]

Conclusion

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Summary

Reviewer

The Code Learners

Review Date

2020-11-24

Reviewed Item

Javascript Object.keys() Method - Get Array of keys from Object and Array

Author Rating

Software Name

Javascript Programming

Software Name

Windows Os, Mac Os, Ubuntu Os

Software Category

Web Development