check property exist or not in javascript code example

Example 1: how to check wether the property exist in a object in java script

if (obj.hasOwnProperty('prop')) {
    // do something
}

Example 2: javascript does object have property

var person = {'first_name': 'bill','age':20};

if ( person.hasOwnProperty('first_name') ) {
    //person has a first_name property
}