Why float becomes string in javascript

Question

I have this code in javascript:

var childrenSize = 7;

    var flAmt = parseFloat(100);
    var amt   = parseFloat(flAmt/childrenSize);

    //Rounding-off fix
    var newAmt = (amt.toFixed(2))*childrenSize;
    alert(newAmt);
    var excess = 0;
    if(newAmt != flAmt)
        excess = parseFloat(flAmt - newAmt);
    amt = parseFloat(amt) + excess.toFixed(2);
    alert(amt);

amt should be 14.25. But instead, it becomes 14.285714285714286-0.03... why?
Also, how can I improve my code?

"amt should be 100" Why? You divide 100 by 7.

j08691
– j08691

2014-10-27 14:52:48 +00:00
Commented Oct 27, 2014 at 14:52 — j08691
– j08691, Commented Oct 27, 2014 at 14:52
What result are you expecting? jsfiddle.net/5zr7fz0z

l'L'l
– l'L'l

2014-10-27 14:53:21 +00:00
Commented Oct 27, 2014 at 14:53 — l'L'l
– l'L'l, Commented Oct 27, 2014 at 14:53
@j08691 it should be amt should be 14.25

newbie
– newbie

2014-10-27 14:57:03 +00:00
Commented Oct 27, 2014 at 14:57 — newbie
– newbie, Commented Oct 27, 2014 at 14:57
@newbie Did my answer solve your question?

User
– User

2014-11-16 07:27:16 +00:00
Commented Nov 16, 2014 at 7:27 — User
– User, Commented Nov 16, 2014 at 7:27

User · Accepted Answer · 2014-10-27 15:02:48Z

2

The toFixed function returns a string, so using the + operator performs a string concatenation instead of an addition.

To get the value of 14.26 which you were (almost) expecting, call toFixed after the addition, like so:

amt = (parseFloat(amt) + excess).toFixed(2);

However, amt is already a float, so is doesn't seem as though parseFloat is needed here.

edited Oct 27, 2014 at 15:02

answered Oct 27, 2014 at 14:53

User

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2 Comments

James Donnelly Over a year ago

Worth noting that you can convert it back to a number by placing a Unary Plus (+) symbol in front of it like so: +(excess.toFixed(2)).

BeNdErR Over a year ago

see docs here: toFixed

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