Can anyone help me? I've got what seems to be just a basic 'math doesn't work' in a conditional.

var marginDelta = (parseFloat(fbaContributionMarginAmt) - parseFloat(fbmContributionMarginAmt)).toFixed(2);

    logModule.debug({title: 'Margin Delta', details: marginDelta});
    logModule.debug({title: 'FBM Margin', details: fbmContributionMarginAmt});
    logModule.debug({title: 'FBA Margin', details: fbaContributionMarginAmt});

if (fbaContributionMarginAmt > fbmContributionMarginAmt) {  //in example if 5.73 > 10.02 which... it's not.
    rec.setValue({fieldId: 'custrecord_br_cst1_margin_review', value: true}); //box is being checked
    rec.setValue({fieldId: 'custrecord_br_cst1_memo', value: 'Difference of: ' + marginDelta}); //gives a negative value
}

Log: Title Details FBA Margin 5.73 FBM Margin 10.02 Margin Delta -4.29 But it's filling the fields with:

the guess is that fbmContributionMarginAmt and fbaContributionMarginAmt are strings

They're formatted with parseFloat earlier in the code. I've done them as parseFloat at the conditional level with the same result... Should have mentioned. And they are subtracting to give the -4.29. Strangely, if our test margins are both negative, it works fine.

do

var fbaContributionMarginAmt = 5.73;
var fbmContributionMarginAmt = 10.02;

var marginDelta = (fbaContributionMarginAmt - fbmContributionMarginAmt).toFixed(2);

    logModule.debug({title: 'Margin Delta', details: marginDelta});
    logModule.debug({title: 'FBM Margin', details: fbmContributionMarginAmt});
    logModule.debug({title: 'FBA Margin', details: fbaContributionMarginAmt});

if (fbaContributionMarginAmt > fbmContributionMarginAmt) {  //in example if 5.73 > 10.02 which... it's not.
    rec.setValue({fieldId: 'custrecord_br_cst1_margin_review', value: true}); //box is being checked
    rec.setValue({fieldId: 'custrecord_br_cst1_memo', value: 'Difference of: ' + marginDelta}); //gives a negative value
}

Yeah. That worked.

You didn't format them with parseFloat, you temporarily casted them

huh. I've never heard of that. I have research to do!

you need to share more code to see whats wrong

I think I understand. Is it that they didn't maintain their 'formatting' (casting) inside the conditional loop?

but either you dont know how to tell the difference between a string and a number

Because I just re-cast(?) them and it worked when I did it inside the conditional

or you dont know how toFixed works

I don't know how toFixed works. As soon as I clicked that link I realized.

you also generally dont want to use parseFloat or parseInt on Numbers

Oh, I totally see that now. It's all Math. I've been turning them back and forth into strings!