hasOwnProperty()  Object  instance method JS Home  <<  JS Reference  <<  Object  <<  hasOwnProperty()

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Description

Returns a boolean indicating whether the object has the specified direct property.

• Only direct properties return boolean true.
• Anything else including methods inherited via the prototype chain such as toString() return boolean false.

Syntax

Parameters

None.

Examples

The code below creates a custom object type function and checks the hasOwnProperty() method in it and properties inherited from the prototype chain.

// Define a custom object type function.
function HomeOwner(firstName,lastName) {  
  this.firstName=firstName;  
  this.lastName=lastName;  
}  

// Check direct properties.
owner = new HomeOwner('Barney','Magrew');  
alert(owner.hasOwnProperty('lastName')); // exists so should be true

// Delete lastName property
delete owner.lastName;  
alert(owner.hasOwnProperty('lastName')); // deleted so should be false

// Check inherited  property
alert(owner.hasOwnProperty('toString')); // inherited so should be false

Related Tutorials

JavaScript Basic Tutorials - Lesson 7 - Objects

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