Answers for "js object property how to use a string to see if property exists"

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

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

javascript check if object property exists

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

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