Javascript parseFloat and nulls

Question

I am very new to javascript as I am currently making a cross platform web app in jQuery Mobile, I have used the example of XML Parsing to a HighCharts graph yet when I encounter a null in my series data it fails to draw any of the line and makes it into a scatter plot almost.

// push data points
$(series).find('data point').each(function(i, point) {
    seriesOptions.data.push( 
        parseFloat($(point).text())
    );
});

I have no idea how to write a if statement that checks to see if it found a null and if so how to tell it to use it... Can anyone please help or point me in the right direction as I would love my charts to be correct rather than placing a zero value where I have a null.

score 9 · Answer 1 · answered Mar 18 '13 at 15:54

9

Well, parseFloat will return 'NaN' if it's not a number (null and undefined are NaNs) so you could try doing like this:

// push data points
$(series).find('data point').each(function(i, point) {
    var floatVal = parseFloat($(point).text());
    if (!isNaN(floatVal)) {
        seriesOptions.data.push(floatVal);
    }
});

answered Mar 18 '13 at 15:54

Björn Roberg

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2
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Thank you for the reply Bjorn - I have put this in place and it works but not quite as intended for the charting, I need the value that comes back to reference either a number or the word null for HighCharts to plot a blank where the null lies. Would this then require converting the NaN to a null or am I completely way off? I have heard of isNull before but not isNaN... – Palendrone Mar 18 '13 at 16:03

score 1 · Answer 2 · answered Mar 18 '13 at 14:00

1

A null check in JavaScript if just like any other C-style language:

 if (thing == null)

Or

 if (thing != null)

I find this works well in most cases against my own programming where I'm writing as I would in, say, C#; however I find other peoples code relies on things never having been declared or set and such and so, and, all in all, it boils down to a spaghetti of checking for null and "undefined" - yes, the literal string, really - and whatever else.

answered Mar 18 '13 at 14:00

Grant Thomas

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Many thanks for your reply, what you have put makes some sense but I am really at a loss as to where this fits in with where I need to check for the null in my code - as I say I am very new to this and so far managed to piece what I need together to get to the end result. Would you be so kind as to help me where it goes with the function outlined? – Palendrone Mar 18 '13 at 15:33

score 0 · Accepted Answer · answered Mar 18 '13 at 16:15

With a quick google on Javascript If statments I beleive I have got there - thanks Bjorn :0) Your answer led me to get there !!!

// push data points
$(series).find('data point').each(function(i, point) {
    var floatVal = parseFloat($(point).text());
            if (!isNaN(floatVal)) {
                seriesOptions.data.push(floatVal);
        }
        else {
        seriesOptions.data.push(null);
        }
        console.log(floatVal)
    });

Nice! I'm glad that you found the answer! :) – Björn Roberg Mar 19 '13 at 06:52 — Björn Roberg, Mar 19 '13 at 06:52

Javascript parseFloat and nulls

3 Answers3

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