var person = {
"first_name": "Bob",
"last_name": "Dylan"
};
person.hasOwnProperty('first_name'); //returns true
person.hasOwnProperty('age'); //returns falsevar person = {'first_name': 'bill','age':20};
if ( person.hasOwnProperty('first_name') ) {
//person has a first_name property
}
The hasOwnProperty() method returns a boolean indicating whether the object has the specified property as its own property (as opposed to inheriting it).
const object1 = {};
object1.property1 = 42;
console.log(object1.hasOwnProperty('property1'));
// expected output: true
console.log(object1.hasOwnProperty('toString'));
// expected output: false
o = new Object();
o.propOne = null;
o.hasOwnProperty('propOne'); // returns true
o.propTwo = undefined;
o.hasOwnProperty('propTwo'); // returns true
// JavaScript does not protect hasOwnProperty method
var foo = {
// overriding foo's default hasOwnProperty method
hasOwnProperty: function() {
return false;
},
bar: 'data'
};
foo.hasOwnProperty('bar'); // false always
// Hence, to prevent this, use Object.prototype.hasOwnProperty as follows-
Object.prototype.hasOwnProperty.call(foo, 'bar'); // truevar x = {
y: 10
};
console.log(x.hasOwnProperty("y")); //true
console.log(x.hasOwnProperty("z")); //false