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()
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.
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
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 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
Conclusion
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