Mastering JavaScript

Chapter 1
I recommend that you read the exhaustive answer on Stack Overflow (http://
stackoverflow.com/questions/588004/is-floating-point-math-broken) and
(http://floating-point-gui.de/), which explains why this is the case. However,
it is important to understand that floating point arithmetic should be handled with
due care. In most cases, you will not have to rely on extreme precision of decimal
points but if you have to, you can try using libraries such as big.js (https://
github.com/MikeMcl/big.js) that try to solve this problem.
If you intend to code extremely precise financial systems, you should represent $
values as cents to avoid rounding errors. One of the systems that I worked on used
to round off the Value Added Tax (VAT) amount to two decimal points. With
thousands of orders a day, this rounding off amount per order became a massive
accounting headache. We needed to overhaul the entire Java web service stack and
JavaScript frontend for this.
A few special values are also defined as part of the Number type. The first two are
Number.MAX_VALUE and Number.MIN_VALUE, which define the outer bounds of the
Number value set. All ECMAScript numbers must fall between these two values,
without exception. A calculation can, however, result in a number that does not
fall in between these two numbers. When a calculation results in a number greater
than Number.MAX_VALUE, it is assigned a value of Number.POSITIVE_INFINITY,
meaning that it has no numeric value anymore. Likewise, a calculation that results
in a number less than Number.MIN_VALUE is assigned a value of Number.NEGATIVE_
INFINITY, which also has no numeric value. If a calculation returns an infinite value,
the result cannot be used in any further calculations. You can use the isInfinite()
method to verify if the calculation result is an infinity.
Another peculiarity of JavaScript is a special value called NaN (short for Not a
Number). In general, this occurs when conversion from another type (String, Boolean,
and so on) fails. Observe the following peculiarity of NaN:
EN-VedA:~ $ node
> isNaN(NaN);
true
> NaN==NaN;
false
> isNaN("elephant");
true
> NaN+5;
NaN
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