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I'll admit I'm weak in JavaScript and JSON. I've spent a lot of time attempting to figure out why numbers from my objects returns NaN when they are added together. With that in mind, below is my JSON, stored to a variable:

var data = [
    {
        "acc_ext_id": null,
        "cat_code": 10002,
        "cat_ds": "REVENUE",
        "category_id": null,
        "chart_id": null,
        "created_at": null,
        "dept_id": null,
        "feb": null,
        "id": null,
        "jan": 30,
        "note": null,
        "total_cost": null,
        "updated_at": null,
        "year_id": null
    },
    {
        "acc_ext_id": "41260-02600",
        "cat_code": 10002,
        "cat_ds": "REVENUE",
        "category_id": 2,
        "chart_id": 2373,
        "created_at": "2013-01-15 16:43:52.169213",
        "dept_id": 86,
        "feb": 45,
        "id": 3,
        "jan": 60,
        "note": "Two",
        "total_cost": 105,
        "updated_at": "2013-01-15 16:43:52.169213",
        "year_id": 1
    }
]

I then attempt to iterate over the objects and sum the values:

var jan;

for (var i=0;i<data.length;i++){ 
    if(data[i].jan != null){    
        jan += parseFloat(data[i].jan);
        console.log(jan);
    }
}

Printed out in the console is NaN. I've attempted to parse the number as well as leave it raw, but to no avail. Is there something wrong with my objects? Here is a jsFiddle to illustrate: /

I'll admit I'm weak in JavaScript and JSON. I've spent a lot of time attempting to figure out why numbers from my objects returns NaN when they are added together. With that in mind, below is my JSON, stored to a variable:

var data = [
    {
        "acc_ext_id": null,
        "cat_code": 10002,
        "cat_ds": "REVENUE",
        "category_id": null,
        "chart_id": null,
        "created_at": null,
        "dept_id": null,
        "feb": null,
        "id": null,
        "jan": 30,
        "note": null,
        "total_cost": null,
        "updated_at": null,
        "year_id": null
    },
    {
        "acc_ext_id": "41260-02600",
        "cat_code": 10002,
        "cat_ds": "REVENUE",
        "category_id": 2,
        "chart_id": 2373,
        "created_at": "2013-01-15 16:43:52.169213",
        "dept_id": 86,
        "feb": 45,
        "id": 3,
        "jan": 60,
        "note": "Two",
        "total_cost": 105,
        "updated_at": "2013-01-15 16:43:52.169213",
        "year_id": 1
    }
]

I then attempt to iterate over the objects and sum the values:

var jan;

for (var i=0;i<data.length;i++){ 
    if(data[i].jan != null){    
        jan += parseFloat(data[i].jan);
        console.log(jan);
    }
}

Printed out in the console is NaN. I've attempted to parse the number as well as leave it raw, but to no avail. Is there something wrong with my objects? Here is a jsFiddle to illustrate: http://jsfiddle.net/5E2pm/3/

• javascript

Share Improve this question Follow edited Jan 20, 2013 at 6:35 Derek 朕會功夫 94.3k4545 gold badges195195 silver badges253253 bronze badges asked Jan 20, 2013 at 6:16 groc426groc426 31922 gold badges33 silver badges1111 bronze badges 1

• 2 That's not JSON, it's an object. undefined plus any number gives NaN. – nnnnnn Commented Jan 20, 2013 at 6:20

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3 Answers 3

Sorted by: Reset to default 15

var jan = 0; //this should solve it

for (var i=0;i<data.length;i++){ 
    if(data[i].jan != null){    
        jan += parseFloat(data[i].jan);
        console.log(jan);
    }
}

Try this should solve it :)

Explanation as quoted by DON in comments below:

var jan; this will declare variable as undefined, so when you try to add values with undefined you will get as NaN, so the answer here with var jan = 0 will work – DON

2021

This is a good use for a reducer

const jan = data.reduce(function(total, current) {
 return total + current.jan;
}, 0); // starting value

OLD ANSWER

I like this approach. It basically sets the value to 0 on the first iteration when jan doesn't exist.

jan = (jan || 0) + parseFloat(data[i].jan);

you need to initialize jan first

var jan = 0; 

here's the example - link

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