Not able to check if variable is null

Question

I have a json response as follows:

response:{
    attempts: 0,
    created_at: "2015-03-03 20:05:50",
    created_by: null,
    deleted_at: null,
    display_name: null,
}

In JavaScript, i've checked it as follows:

if(data.response.display_name!=null){
    return toTitleCase(data.response.display_name);
}

According to the above code, display_name should never have passed to toTitleCase. However, the above condition is validated as false and hence a null object is passed to the function. Looking around here, I found this: https://stackoverflow.com/a/26330848/1411975

However, trying that as

if(data.response.display_name!='null'){
    return toTitleCase(data.response.display_name);
}

also gave me errors. How do I check if the value is null? I don't have control over the incoming data so there's no way I can change that to undefined.

EDITS: Any extra information I've missed out.

The server is in Laravel if that makes a difference and the values are being picked from a MySQL db.
The response object as pasted above is correct.

Console.log for data.response

attempts: 0
created_at: "2015-03-03 20:05:50"
created_by: null
deleted_at: null
display_name: null

Console.log for data.response.display_name
```
null
```
Error on using second method:
```
TypeError: Cannot read property 'replace' of null
```
Since toTitleCase has a replace() method implemented.

EDIT[2]:

 function returnUsername(data){
    if(data.response.display_name !="" || data.response.display_name!=null){
        return toTitleCase(data.response.display_name);
    }else{
            return toTitleCase(data.response.username);
    }
}
function toTitleCase(str){
    return str.replace(/\w\S*/g, function(txt){return txt.charAt(0).toUpperCase() + txt.substr(1).toLowerCase();});
}

Full trace:

TypeError: Cannot read property 'replace' of null
at toTitleCase (app.js:850)
at returnUsername (app.js:842)
at app.js:498
at angular.js:8148
at l.promise.then.J (angular.js:11659)
at l.promise.then.J (angular.js:11659)
at angular.js:11745
at h.$get.h.$eval (angular.js:12788)
at h.$get.h.$digest (angular.js:12600)
at h.$get.h.$apply (angular.js:12892)

Put a console.log right before that if...are you positive it's `null`? — tymeJV, Mar 03 '15 at 14:43
possible duplicate of [JavaScript checking for null vs. undefined and difference between == and ===](http://stackoverflow.com/questions/5101948/javascript-checking-for-null-vs-undefined-and-difference-between-and) — Steve Mitcham, Mar 03 '15 at 14:44
@tymeJV Hi, I've put a console.log there. I'm absolutely positive it's null. The log shows `null`. — Newtt, Mar 03 '15 at 14:46
Trying your exact code, it works as expected. The object that's being evaluated must be different than the one you pasted in the question. http://jsfiddle.net/8nyb9kf0/ — Tom, Mar 03 '15 at 14:46
are you sure your data is correct, works fine for me: http://jsfiddle.net/faatyqm7/1/. What happens if you console.log `data.response` — Pete, Mar 03 '15 at 14:47
Can you post your complete code and the complete stack trace? I don't think the error stems from your `toTitleCase` function — Bergi, Mar 03 '15 at 14:58
How about `typeof (data.response.display_name || null) !== 'null'` — D-Bennett, Mar 03 '15 at 17:14

Not able to check if variable is null

0 Answers0