CODEWITHSUNDEEP
javascriptjqueryarraysjson
tamasys
tamasys

Reputation: 59

Shorthand for checking if array element is defined

I'm trying to add together a bunch of elements in a decoded JSON array:

var jqXHR = $.getJSON("data.php", function(jsonData) {
    newItems      = jsonData['New']['count'] || 0;
    unsolvedItems = (jsonData['New']['count'] || 0)+
                    (jsonData['b']['count'] || 0)+
                    (jsonData['c']['count'] || 0)+
                    (jsonData['d']['count'] || 0)+
                    (jsonData['e']['count'] || 0)+
                    (jsonData['f']['count'] || 0)+
                    (jsonData['g']['count'] || 0);
}

As you can see, I'm trying to check if the ['count'] element exists before I try and assign the value to something, using the shorthand explained on this site, but the || 0 shorthand doesn't seem to be working. When ['New'] is not included in the JSON, I get Uncaught TypeError: Cannot read property 'count' of undefined.

Does this not work on arrays, or am I doing it wrong? If it doesn't work, what else could I do other than resorting to a separate if statement for every element I want to use?

Upvotes: 0

Views: 1330

Answers (2)

adrichman
adrichman

Reputation: 1235

the pattern that I usually opt for:

jsonData['b'] && jsonData['b']['count'] || 0

Upvotes: 0

Denys Séguret
Denys Séguret

Reputation: 382384

The problem is that you can't get jsonData['d']['count'] if jsonData['d'] is undefined.

Your code is also full of repetitions. This kind of code is painful to maintain.

You could do it like this :

unsolvedItems = 0;
['New','b','c','d','e','f','g'].forEach(function(key){
    if (jsonData[key]) unsolvedItems += jsonData[key].count || 0;
});

Upvotes: 2

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