Summary: JavaScript amount calculation

Today in the project to develop a calculation of the amount of functionality, I started to do this:

eg

var amount + = parsefloat (0.01+0.02);

Results: 0.0300000000000000001

Why is it?

Search the parsefloat theme:

1. The parsefloat () function---Parse string---returns a floating-point number.

During the parsing process, I encountered

plus sign (+ or-),

Numbers (0-9),

Decimal point

Index in science notation (e or E)

　　other than the characters ,

It ignores the character and all subsequent characters. Whitespace characters at the top of the parameter string are ignored.

The first character cannot be parsed into a number---"returns NaN.

Well..... Feeling or understanding is not deep, why would be so a long string, precision problems, see how the principle ....

But..... Didn't find a clear explanation of the underlying

Let's take a look at the solution for a moment:

(1)

ToFixed (n) But this method is not compatible with JS version requirements IE5

(2)

var price = 5.02
var quantity = 4
var amount= math.round (parsefloat (price*100 *quantity))/100;

Math.ceil () is rounding up
Math.floor () is rounded down
Math.Round () is rounded

Welcome to provide solutions, answer doubts ....

Summary: JavaScript amount calculation