How to get 12.6 with a=10.3 and b=2.3?

Question

var a=10.3;
var b=2.3;
alert(a+b);

but I get 12.600000000000001. I know JavaScript is loosely typed, but I hope I can do a sum :)

so your question is about formatting a number with a limited number of decimals? — Dan D., Feb 14 '12 at 08:51
This inaccuracy is rather due to how [floating point numbers are represented in binary](http://www.google.com/search?What%20every%20computer%20scientist%20should%20know%20about%20floating-point%20arithmetic). — Gumbo, Feb 14 '12 at 08:55

score 2 · Answer 1 · answered Feb 14 '12 at 08:56

2

you can use toFixed() method also

var a=10.3;
var b=2.3;
alert((a+b).toFixed(1));

Works in chrome

answered Feb 14 '12 at 08:56

Raghuveer

2,630
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29
59

score 1 · Accepted Answer · answered Feb 14 '12 at 08:53

1

Multiply to the precision you want then round and divide by whatever you multiplied by:

var a=10.3;
var b=2.3;
alert(Math.round((a+b) * 10) / 10);

http://jsfiddle.net/DYKJB/3/

answered Feb 14 '12 at 08:53

Richard Dalton

35,513
6
73
91

score 1 · Answer 3 · answered Feb 14 '12 at 08:55

It's not about the typing but about the precision of floating point types. You need to round for presentation.

Floating point types are not a good choice if you need exact values. If you want to express currency values express them as cents or use an appropriate library for this.

How to get 12.6 with a=10.3 and b=2.3?

3 Answers3