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

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

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

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"]
With Object.defineProperty() method
With Object.defineProperty() method

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
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 Object.keys() method with array
Using Object.keys() method with array

Using string on `Object.keys()

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

//Console Output
(10) ["0", "1", "2", "3", "4", "5", "6", "7", "8", "9"]
Using Obejct.keys() on string
Using Obejct.keys() on string

Conclusion

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