How to check if my json array has missing objects

Question

i am having and json file wich is created dynamicaly.

For example

{
    "users": [
        {
            "name": "Bill",
            "surname": "Antony",
            "userPoints": 121,
            "wins": 11,
            "nationality": "English"
        },
        {
            "name": "George",
            "surname": "Peter",
            "userPoints": 1332,
            "wins": 11
        }
    ]
}

As you can see the second object is missing nationality field. So in my code when i am printing with JS Jquery (.each). I am having an 'undedified' print for the second user. How can i check this before it's printed?

EDIT: I am adding the way i am printing the data:

function displayData(array) {
    var list = $("#list").empty();
    $.each(array, function () {
       $("ul").append('<li><span class="num">'+ if(this["nationality"]){ this["nationality"] }+'</span></li>');
    });
}

Loop through it ahead of time and make sure none of the expected properties are undefined? — Andrew McGivery
– Andrew McGivery, Commented Jun 25, 2014 at 18:59

Rory McCrossan · Accepted Answer · 2014-06-25 18:59:13Z

4

undefined equates to false, so you can check the property of the object like this:

$.each(data.users, function(i, item) {
    if (item.nationality) {
        console.log(item.nationality);
    }
});

You could also shorten the if statement to this and get the same result:

item.nationality && console.log(item.nationality);

answered Jun 25, 2014 at 18:59

Rory McCrossan

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3 Comments

Afzaal Ahmad Zeeshan Over a year ago

+1, I never knew undefined == false. Good information.

Rory McCrossan Over a year ago

@AfzaalAhmadZeeshan Yep, it's a handy quirk of javascript. More info: sitepoint.com/javascript-truthy-falsy

Rory McCrossan Over a year ago

You can't use an if statement within a string concatenation like that.

Kristoffer Jälén · Accepted Answer · 2014-06-25 19:03:19Z

1

You can use hasOwnProperty(). Documentation.

if(users[0].hasOwnProperty('nationality')){

}

answered Jun 25, 2014 at 19:03

Kristoffer Jälén

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4 Comments

Vassilis Pits Over a year ago

Thank you! That was the solution! Is there anyway to make it search all the fields instead of doing it for one each time?

Kristoffer Jälén Over a year ago

Well, somehow you need to know what properties to search for. If you know that, you can just iterate through the properties.

Vassilis Pits Over a year ago

Ah allright, so i have to make multiple if statements. That's ok i guess! Thanks again!

Kristoffer Jälén Over a year ago

Or you can put the properties in an array, and loop through that.

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