Use of plus sign "+" is adding text, not performing mathematical addition

[michaelwm25]

I'm working on a little project to display recorded data from quadcopter flights on video and am very new to writing expression code.  I have the fundamentals working as desired, but I am having issues while trying to add "fine tuning" capabilities such as biasing the recorded data.  To try and achieve biasing,  I created a slider effect "HeadingAdjustment" to set the desired bias value and used the following expression to try and add that bias value to the data pulled from the "DataSource" csv file:

var Heading = (footage(DataSource).dataValue([21, DTime]).toFixed(0) + thisComp.layer("Globals").effect("HeadingAdjustment")("Slider"));

Lets say  the recorded data is "95" and the HeadingAdjustment slider is set to 10.  I want the data displayed to show "105", but it shows "9510" ("10" appended to "95") instead.

How do I get the variable definition to perform mathmatical addition rather than adding text / strings?

Thank you!

[michaelwm25]

Wouldn't you know it after some additional searching I find a similar topic "parsing number text string to numeric value" and   learn of add() expresstion. Code that achieves the goal (may not be most efficient, but works):

HeadingData = footage(DataSource).dataValue([21, DTime]).toFixed(0);
HeadingBias = thisComp.layer("Globals").effect("HeadingAdjustment")("Slider");
Heading = add(HeadingData, HeadingBias);

[Roland Kahlenberg · Accepted solution]

Reading data from a dataset is essentially reading a text file. Hence the values you see are in effect just an object to AE.
You'll have to convert the Heading to a number and you use the parseFloat() method to do this.
So, writing like this should work -

var Heading = (footage(DataSource).dataValue([21, DTime]).toFixed(0) ;
parseFloat(Heading) + thisComp.layer("Globals").effect("HeadingAdjustment")("Slider"));

More info on parseFloat() can be found here - https://www.w3schools.com/jsref/jsref_parsefloat.asp

[michaelwm25]

Thank you Roland!  I'll think I'll be using that site frequently in the near future as I learn more.