Javascript values seem to be concaternated and not added together

Question

I have a function which job is to get a total from values from an array, however it doesn't work. EG. my array looks like

    [["10", "", ""], ["10", "", ""], ["10", "", ""]]

So the value i am expecting is 30 however i am getting 0101010 in console.log

function createAv(results){
    var av = results;

    var a1 = 0;
    var a2 = 0;
    var a3 = 0;

    function percentage(av){
    var n1 = 0;
    for (var index = 0; index < av.length; index++) {

            n1 += av[index][0];
        a1 = (av[0][0] / n1) * 100; 
        a2 = (av[1][0] / n1) * 100; 
        a3 = (av[2][0] / n1) * 100; 
    }
      return n1;
    }

    var test = (percentage(av));

    return test;

  }

Josh Earl · Answer 1 · 2012-03-08T18:10:14.093

3

The values in your array are strings, so JavaScript is concatenating them. Try using parseInt() to change the array values to numbers.

Here's a jsFiddle that illustrates how to do this.

edited Mar 08 '12 at 18:10

answered Mar 08 '12 at 18:03

Josh Earl

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score 3 · Answer 2 · answered Mar 08 '12 at 18:04

3

Your array of values are strings, try converting them into integers like so.

n1 += Integer.parseInt( av[index][0]);

or change your array like so

[[10, 0, 0], [10, 0, 0], [10, 0, 0]]

answered Mar 08 '12 at 18:04

Kingpin2k

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The array is created dynamically from input boxes so they come in as strings. Could parseInt convert the whole array into integers? – kishan patel Mar 08 '12 at 18:16
@kishan: You could use `parseInt` to convert the values *before* you add them to the array. – Felix Kling Mar 08 '12 at 18:26

score 1 · Accepted Answer · edited Mar 08 '12 at 18:38

1

It's because the numbers are in strings. You can add strings to other strings (and even add numerical values to those strings), but you'll end up with a concatenated string.

If they need to be strings, that's OK - you can use parseInt() to treat them like numbers.

for (var index = 0; index < av.length; index++) {

    n1 += parseInt(av[index][0], 10);

    a1 = (parseInt(av[0][0], 10) / n1) * 100; 
    a2 = (parseInt(av[1][0], 10) / n1) * 100; 
    a3 = (parseInt(av[2][0], 10) / n1) * 100; 
}

edited Mar 08 '12 at 18:38

hugomg

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answered Mar 08 '12 at 18:03

Surreal Dreams

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I need them to be all integers really because i will be doing mathematical operations on them. Could i use parseInt to convert the array into an integer array? – kishan patel Mar 08 '12 at 18:12
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@kishanpatel: `av = av.map( function(v,i) { return v.map(Number); });` – Mar 08 '12 at 18:35
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Don't forget to add a base parameter to parseInt: `parseInt(str, 10) `. Otherwise if bugs out on things with leading zeroes, things like "09" – hugomg Mar 08 '12 at 18:38
@missingno that's an excellent point, and considering that the "numbers" here are strings, unintentional leading zeros are a definite risk. Good call. – Surreal Dreams Mar 08 '12 at 19:17

score 1 · Answer 4 · answered Mar 08 '12 at 18:05

1

You can try casting it as a int

n1 += parseInt(av[index][0]);

answered Mar 08 '12 at 18:05

Manatok

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Javascript values seem to be concaternated and not added together

4 Answers4